We did what we called "touch training" for at least 30 mins each day with our lovebird once she started getting really nippy.
She was barely handled when hand raised so she never liked hands to begin with but just after a couple weeks training I could pick her up in my hand upside down and give her scratches around her beak.
Unfortunately she still attacks a few random people that visit (Usually people giving off very obvious fear), so I'm currently getting my friends to touch train her as well to curve her dominance.
We started with making her have to go under our hand on a long perch to get a seed.
After she was comfortable with that we lowered our hand until it was nearly touching her then repeated.
After a couple sessions we made it that she had to squeeze under our hand to get the seed that was held under it and gave the verbal command "go under my hand" in a calm friendly voice.
Now we can just tell her to go under our hand and she will run under even without food.
We also did beak touching which started with slowly making contact with her beak with the tip of our finger and rewarding her for not biting.
Our touch training now involves -Rubbing all around the beak, Gently extending each wing, checking feet and fingernails and also laying them on their back in our palm.
Daily training in general will dramatically reduce biting in most parrots though I found these methods to be the most effective if taken slowly with no other people or distractions around.
To get to that point so you can do touch training just spend time with him giving him sunflower seeds or a similar favored treat but don't let him get them from anywhere else ever, so he can't resist taking them from you.
If he does ever bite don't make a fuss and definitely don't take him to your boyfriend as he could be part of the problem, they can get very protective of one person. Yelling or dramatic reactions also just gets them excited and can increase the aggression. Just simply tell him "no biting" (while fighting back the rage and pain) then put him on a simple boring perch and turn your back on him for a short period. Once calm turn around pick him up (once you can obviously) and start over like nothing happened. If he ever bites to get your attention try ignore it completely just like you would if he is squawking loudly for no reason.
I have also read when they start nipping for no reason at a young age don't ever move your hand away no matter how painful as moving it just reinforces that biting gets rid of hand.
Good luck
