Out of all the dog behavioral problems, biting is considered to be the worst and the most serious. Even if your dog goes on the couch quite often, it might not present you as much problem as from a biting behavior. Some communities insist on putting the dog down if he bites someone severely. If your dog has a biting problem it can even mean the end of his life. So you have to take immediate action to solve the biting problem of your dog.
On the other hand, biting problems are common and quite normal in case of puppies. This problem arises mostly during their teething period when they have an uncontrollable urge to chew and bite on anything and everything. Though a puppy bite might break your skin it will not pose any other serious problems. However, this is the right time and age to train your puppy not to bite ever again