My girl is in the biting/chewing stage herself (she's about 14wks), most of the time it doesn't bother me much cause she more mouths me than bites, when she gets excited she'll bite harder. I usually ball my hands when she starts biting too hard and she gradually eases up some cause she can't get to my fingers and gets bored
Sometimes if she hurts me by surprise, I'll yelped like I normally do with a loud "ouch" or make a sharp "no" and it startles her to stop. Otherwise, she sometimes sort of mouths me because it's comforting to her (like a pacifier) and she'll be real gentle too.
Poking/pinching her never helps, and I believe this is for most dogs, as it only makes her want to get at me more cause to her it's play or she's telling me she doesn't like it. The way she does it, I don't believe she's being aggressive as much as trying to play or get that teething thing going. I have two older jack russell dogs and one she's a bit more careful and respectful towards cause that one will snap/growl at her to keep her in her place, but she's never hurt her, mostly startled her. The other younger JR usually lets her do whatever to her and she'll play mouth with her. My yorkie baby likes to try to ride on her ^^; (laying her upper body on the older dog and move with her while she walks) only thing is they're both now starting to be about the same size ^^;;
I would say one good way to try to deter that behavior is to stop what your doing, get up and leave, also ignore him for a little bit everytime he gets that way with you. Or maybe distract him with something else. Or you might try a sort of bribe method, have some treat he really likes and don't give it to him until he does what you want. If he bites, he doesn't get a treat, if he's calm (maybe start training him to sit) then treat. My girl has learned to sit on command, but she'll mostly do it if you have or she thinks you have something she wants ^^;