1) Don't say "No." Without aversive consequences it doesn't help or is even counter productive. It's like one of those kids toys that say "press here" and it talks. The bird learns to "bite here" to get the human to respond.
2) You're not the boss. You never will be the boss. The parrot will always think it is the boss. The best you can hope for is flock mate and get the parrot to respond to you because it wants to for positive reinforcement.
3) Don't towel. This will only make the parrot fearful of the towel and most likely more aggressive.
4) The parrot is probably hormonal but also maturing. It is becoming more independent and realizing that it doesn't have to come out just because you want it to and biting is the way to do it. Most likely it is your fault and you taught it to bite. It could just be a phase and things might go back on their own, but this is not guaranteed. The parrot is obviously maturing and experimenting, testing it's independence so to say. If this phase is handled incorrectly, it may learn to stay that way long term.
5) But don't worry, it is still possible to amend this situation. First off you're going to have to make sure that all out of cage experiences are positively reinforcing. The parrot should look forward to coming out instead of being defensive.
6) Go back to basics and retame. This is a good exercise and can be needed from time to time with any parrot. Here are a couple articles about taming which you can follow to rekindle your relationship with parrot and help maintain it:
http://TrainedParrot.com/Taminghttp://theparrotforum.com/viewtopic.php?f=11&t=227http://theparrotforum.com/viewtopic.php?f=18&t=768http://theparrotforum.com/viewtopic.php?f=11&t=1528