First of all I would like to say that it may not just be a phase if the problem is not corrected. Sure some puppies go through this stage, but I have seen ALOT of puppies grow up into adults and still have this problem. Your best bet is to treat it like it is a behavior problem, this way you can correct it and you won't have to worry about him doing it as an adult. Tell him no or no bite in a firm voice. If he does it again move away from him and ignore him for a few minutes or put him in a time out.
What you want to teach him is that biting is not acceptable and that he will not get to play with you or anyone if he bites, if he does not bite he is rewarded with lots of attention and of course playtime with you.
This might sound weird but when he bites you yelp like a wounded puppy in a high pitch voice or you can just say yipe in a high pitch voice, it is soooo much more effective than just saying no. Puppies are learning and testing their strength and skills out on one another.
If you ever watch puppies you will see that if one gets too rough the puppy will yelp and the one that is being rough will back off and learns not to be so rough so that he can play with the other one. It is the same when it comes to puppies and humans. I have trained all of my dogs this way and several other dogs and it works like a charm everytime, you got learn puppy talk!! Good luck on training and let us know how it goes!!!
