I don't like the idea of pinning a young dog. That's not something a novice pet owner should even try.
This problem won't be solved overnight. I have a 9 week old puppy at home right now, and I'm an experienced dog owner. It takes time.
The best advice I can give you is to do what his litter mates, or another dog, would do. When he bites, yelp. Make it loud, and as close to a the sound a dog makes. When you yelp, and he stops, and he will stop, then walk away. Ignore him.
Or, yelp, give him something else to chew on, and then walk away.
The point of this is to get him to stop (the yelp in doggy language means that you're hurt), walking away teaches him that if he bites, you won't play. Giving him something else to chew on teaches him what he's allowed to chew on, and what he's not allowed to chew on.
Most importantly, make sure he has plenty of puppy safe things to chew on. Ice cubes are okay too, and do help with teething, but make sure to supervise, as some puppies are a bit too anxious and can choke on them. Go to your pet store, find someone knowledgeable about puppies, and get some puppy appropriate teething chew toys.
Trust me, this stage won't last forever, and the earlier you start training that this isn't okay, the sooner you'll be nip free.
If you think those puppy teeth hurt when they're in the mouth, wait until they fall out and you step on one that's imbedded into your carpet. I still have nightmares about that.