Hi, My Jack is 6 months old today, and he is finally starting to ease up on the biting. I was beginning to think I had bought a large bat instead of a puppy for awhile. He now just gently bites me when I am playing with him, and when I groom him he actually knaws really softly on one finger.
He has drawn blood a few times, and mainly from us pulling away from him quickly when playing fetch. My vet says to use some tobasco sauce on your finger, and I have had some other Yorkie Yakkers tell me the same thing.
Good luck, and if he starts staying up all night you know you have a bat not a puppy.
Jack and Jill