All puppies play bite and mouth their owners and other pets in the family.  Discourage it because it will continue into adulthood and become painful and unpleasant.

If your pup bites you too hard, even accidentally, stop playing, say “no” or “ah-ah” and walk away. Allow him to calm down and play more quietly next time. If you are consistent he will learn that the consequence of biting is no playmate.