Puppies explore their worlds with their mouths. They taste, chew and nibble on every new thing they come across, and that includes your hand. This can lead to the occasional nip or all-out gnawing whenever you pet them. It's normal. But that doesn't mean chewing or biting should be encouraged.
It's Not Aggression
Dogs are natural hunters born with certain instincts to mouth and chew. For puppies, chewing is play, whether they're chewing on each other while wrestling or on your hands while you pet them. The behavior is not aggressive, but the urge to mouth in puppies is strong, and unless biting behavior is curtailed early, those playful nips with tiny teeth can become painful and even damaging to your hands.
Teach Gentleness
When a puppy bites a littermate too hard, the bitten pup yelps and goes limp for a moment. This immediately signals the mouthy puppy to back off, and the next time she bites her sibling, she won't bite so hard. Teach your pup gentleness by yelping in a high pitch and letting your hand go limp when she bites too hard. She will take that as her cue to play gentler with your sensitive skin, but you may need to repeat this lesson multiple times before it sinks in.
Time Out
The yelp-and-go-limp approach may be effective, but don't use it more than three times within any 15-minute period. If your puppy is not learning to go easier on this schedule, you may need to switch tactics. Just as it does for children, a time out can teach your puppy to not bite so roughly. If he bites too hard, simply get up and ignore him for 10 or 20 seconds, then go back and encourage more play. And be sure to praise him when he plays gently.
Hand Feeding
Feeding your puppy by hand will also teach her how to take food from your hand without biting your skin. This, in turn, will greatly curtail her urge to bite on anyone's hand when being petted. If she bites while eating, simply yelp and withdraw the food and ignore her. Try again in a little while, and when she takes food gently, praise her to reinforce that gently taking food gets the reward and biting the hand removes it.