Hello, and welcome to the Parrot Forums family!
Okay, a lot depends on this bird's background. If he was not hand-raised, it will be a lot tougher to earn his trust than it might be otherwise. 3 weeks is early yet. Just remember that him coming to trust you is a much bigger feat than the other way around. The size difference is probably greater than that of a human to an elephant, for example. So that's a lot of trust.
Best thing is to start off with a lot of bribery. Find out his favorite foods. The stuff he will absolutely lose his mind over. For my birds, cashews and almonds do the trick. Then separate his favorite one or two foods from his general diet. In other words, make it so he can only get these foods from you. And then sit by the side of his cage, between meals when he's feeling a bit hungry, and offer the treat through the bars. Be patient and let him come to you. Might take him a little while to build up the necessary nerve, but eventually he will. And once he does, he will come to associate you with his favorite treat.
Birds learn strongly by association. So you want to take the time to build that link in his mind. Make sure, btw, that you're always talking to him in a mellow voice while bribing him. You want to put him at ease.
As he begins to get more comfortable, you can move on to target training. To start, you can do this through the bars of his cage, basically indicating with a pointer of some kind somewhere you'd like him to go in the cage, and then rewarding him for moving in that direction with his favorite treat. Eventually he'll make the connection and find himself very eager to go where that stick directs him. Here is a link to a video on target training: [ame="https://youtu.be/HaOicTtwIZo"]Beginners guide to target training parrots - YouTube[/ame]
Eventually, once he's at ease with this level interaction, you can open the front of his caged start targeting him somewhere on the outside of his cage. Baby steps. Don't get too eager and try having him fly across the room on your first go. Just a place right beyond the door, like the outside wall of the cage. And then reward with treats and lots of praise.
Now, on to the biting issue. Hopefully much of the biting will subside with the increased interaction and level of trust. For what biting remains, take a good read of this link:
http://www.parrotforums.com/training/57935-brainstorming-biting-parrots.html What I love about that thread is its focus on bite avoidance in general. Many bites are easily avoided if you know what to watch out for.
As for handling any bite that winds up happening anyway, a few tips:
Be proactive. Begin carrying a small, bird-safe piece of wood or hard plastic around with you. (Small enough to carry comfortably in your pocket or even the palm of your hand, and hard enough to withstand a good gnawing.) And then learn the warning signs for when he's about to attack. When he does, interpose the bird-safe item between your flesh and his beak. This will serve the dual purpose of shielding your hand/arm, and also diverting his attention from you as the object of his ire. Most birds will be distracted enough by this that they will momentarily forget their desire to eat you.
Again, once you become more adept at reading his moods, you'll be able to prevent many bites simply by not putting yourself in the position to be bitten in the first place.
Also, when telling him "No", always do so in a calm and even, yet firm, tone of voice. I don't say this to spare Micky's feelings, but rather to make sure that you are not
training him to bite you. You see, when you react animatedly to a nip or bite, he really has no point of reference for your decidedly human body language. So if you yell or jump about cursing and such, it is entirely possible that he might find the display AMUSING. And then he'll of course prove his hypothesis of cause and effect by doing it again. And again. So try your best not to react excitedly. Keep your movements controlled and precise. Keep your voice calm. And use your hand to gently remove his beak from your flesh. (No, don't follow the advice of people who tell you to accept the bite and not react at all. That is just a good way to bleed for absolutely no reason.)
At this point, you would put Micky on timeout for 5 - 15 minutes, making sure to either leave the room completely (if his timeout is in a cage) or turn your back and give no eye contact. Of course, this works best after establishing something of a relationship with the bird as laid out in the steps above. A timeout for a parrot that does not yet have any kind of rapport with you and still actively flees from you is actually a reward. So do everything in its proper order. 1) Build trust and a connection by sharing treats, speaking in a calming voice and keeping your movements deliberate and gentle. 2)Deepen that connection through interactive sessions of target training, first through the bars of the cage and then outside the cage once he's ready. 3) Try targeting him onto your hand. If he's apprehensive, you can use a lure of food that requires him to step onto your finger to reach it. But always remember to let him come to you. It's a good idea if it's HIS idea. Lol!
Here's another link for bite pressure training:
http://www.parrotforums.com/training/63988-bite-pressure-training.html
Hope this helps. Don't hesitate to post with further questions.