Our 8 week old puppy is a biter?

Try giving him a toy like a rope or a bone. Usually puppies do that when they want to play. Give him something he can chew on, and personally I think sticking your finger under their tongue is not going to ever work. If none of that works, then he will probably just grow out of it when he is about a year old. Puppies are usually really playful when they are young.