Biting in puppies is a normal, though undesirable, behavior. Puppies often use their mouths for exploration and play, and this behavior can extend to the human family.
My biggest concern in these situations is that owners may be using or are being told to use physical correction (alpha rolls, leash corrections, holding the mouth closed, pinching the tongue, hitting or tapping the muzzle) as a treatment strategy. Using physical correction can cause a fear response and can result in the escalation of your puppy’s aggressive behaviors.
A better approach is to both address the biting at the time it occurs, and prevent biting as an option for the pup. Once you have ruled out any physical abnormalities that could be contributing to the behavior, your approach should include teaching your puppy simple obedience commands from Day 1, ample playtimes, frequent short leash walks, and puppy socialization classes.