Biting is a dog's capacity to regulate the power with which he bites. While a puppy or dog hasn't acquired bite inhibition with men, he doesn't understand the delicacy of human flesh and bites too forcefully, even when playing. Some behaviorists and trainers feel that if a dog has trained to use his mouth softly while engaging with people, he will be less likely to attack hard and break skin if he ever bites somebody in a non-play scenario, such as when he is scared or in pain.
If your dog bites you while you're playing, entertainment is over, no excuses. As odd as it may sound, yelling at or physically disciplining your puppy is a sort of reward. It educates them that biting elicits a reaction from you, which is known as harsh reinforcement. They may also become frightened of being touched because of this. Instead, educate them that biting will not get them anywhere.