Any avian vet worth their diploma won't have trouble with aggressive birds. My old male amazon is about as aggressive as they get and I have a petite little lady vet who handles him just fine. If his nostril is indeed blocked, you need to just get him there. Your relationship comes secondary to his health and in all honesty, amazons tend to shake things off pretty quickly. If he's a seriously nasty biter, I'd get a heavy blanket off your bed(double it up if necessary) and just reach in the cage and get him. It might not be pretty but its one of those things that just has to be done sometimes even if he ends up doing some heavy breathing and gets stressed. Don't try to be nice about it because you'll just draw out the whole process and stress him out more. Reach in and get him, if you have to chase him around the cage, do it, but make it fast. My birds that are afraid of carriers tend to be more comfortable in the wire dog crates than the mostly plastic airline approved ones. Don't worry about the vet handling him. Research and make sure your taking him to someone that sees birds as a huge percentage of their clientel rather than someone that is just willing to see a bird once in a while. A bird spe******t will think nothing of his antics. A dog and cat spe******t willing to see bird in order to make some money will probably be overwhelmed by him and have no clue how to handle him properly.
In a perfect world, you might be able to put the carrier in his cage loaded with a treat and have him go in on his own. Or he would nicely step up for you and you can sit him on your lap and just calmy wrap him up. That is what a behaviorist would tell you to do. However, the world is rarely perfect and sometimes you just need to get it done. The reality is that if he does indeed have a blocked nostril, there is a decent chance he will end up on medicine and you will just have to get used to toweling him twice a day to get meds into him. If the vet tries to give you a little syringe and medicine and send you on your merry way, stop them right there. Have them teach you how to towel him correctly and have you demonstrate that you can hold his head steady by yourself and give him the first dose in the office. Often times it ends up being a huge fiasco once an inexperienced person gets home with directions to medicate a bird. Most of the time they won't eat it if you put it in their food or they will only eat a portion and you won't know if your getting enough in to be effective. The best way with a crabby bird, is just towel them and make it happen.