Dogs nibble their owners for different reasons, which could include an attempt to show dominance, to signal that the dog is hungry or thirsty or to simply show affection. Dogs characteristically adhere to a hierarchy that reflects the structure of a wolf pack, and biting is a way to assert dominance.
Puppies learn bite inhibition early on in their development. This means that, through playing with litter mates, puppies learn to associate biting with pain. Once the puppy receives a painful bite from a litter mate, it in turn adjusts its bite to get the desired response from the target. If the puppy wants to dominate another litter mate, it increases the pressure of the bite. If for any reason the puppy does not learn bite inhibition early on, this can lead to multiple behavioral problems for the human owner to address and correct.
Nibbling can begin as a seemingly benign behavior in puppies. This behavior points to the possibility that the dog is trying to assert dominance over the owner. Because dogs exist in a pack hierarchy, pet dogs look to their human owners for leadership cues. If the nibbling is tolerated, the dog could modulate its biting habit to increase its level of dominance. If this behavior is not corrected, the dog may continue to nibble or even bite at the owner as it matures.