I would definately start putting an end to the biting. It takes the fun out of playing, doesn't it? I've heard a good way to discipline is to use a squirt bottle and say "no biting" or whatever the problem is. Also, and I have used this method before, use an empty paper towel roll or with a yorkie, a toilet paper roll may be sufficient and pop them. It doesn't hurt, the noise just scares them a little. A small rolled up newspaper or magazine will work, too. Soon, probably all you will have to do is show it to your puppy and it will stop
Hope this helps.