Mouthing and Nipping
Dogs use their mouths as surrogate hands. Mouths are great for picking up, carrying, and tasting things. Dogs also use their mouths to defend themselves or objects they perceive as theirs. While this is all perfectly natural and understandable, your pug must learn that he can never use his teeth on people. In some locales, a single dog bite is enough to require a dog to be euthanized, so teaching your pug not to mouth or bite people is a must.
A pug puppy's lessons in how to use his mouth and teeth begin with his littermates and mother. They yelp loudly or cuff him with their paws if he bites too hard. You can continue that lesson by screeching loudly and then walking away any time your pup bites down too hard on your hand. Remember, dogs — especially pugs — hate being ignored.
Help your pug develop nice mouth manners by offering tiny treats held in your fingers. Again, if you feel his teeth bite down, yell “Ouch” and walk away with the treat. Try again in a couple of minutes and repeat until he learns how to take food gently. (Kids should not try this at home — parents only.)