Every time he bites you yip like a puppy. It sounds silly, but that's how he would learn from his litter mates how not to bite too hard. If that doesn't work, and this is only for extreme cases, get a spray bottle with water or lemon juice or mouthwash, and if he bites you too hard spray it in his mouth. Only use that in really extreme cases and use it sparingly. Be sure if you resort to that, to only spray in his mouth, never near his eyes. Also, be sure he has lots of things he is allowed to chew on, bones, kongs etc because he is teething just like a baby would.Good luck!
Leave some Love!!!