Part of raising a puppy is getting mouthed, nipped or sometimes bitten so hard you want to cry!
It might seem counter intuitive but encourage gentle mouthing from your pup. This way you know how hard his bite is. When his bite gets too hard give your puppy some feedback. The feedback does not necessarily need to be verbal, the verbal ouches and cries will amp many pups up more. Stand up and disengage, turn your back, cross your arms. Make sure you have a leash on the pup so he doesn’t just up and leave the area on you.
Provide something appropriate for the puppy to clamp on to and chew on instead of you. Trade your shirt-sleeve or pant leg for a delicious chew. Ask your puppy to sit. Ask your puppy to leave it. A trade is nice here; give him a good reason to want to leave it.
Practice wild, control exercises. How quick are you able to get your super-charged pup into a sit or a down?
Remember, puppies will bite! Instead of trying to stop the puppy from doing what comes naturally to him, focus on refining your ability to give fair, effective and clear feedback and directing your puppy to something appropriate to chomp on.