Hi and welcome. Here is some reading you probably need if you haven't had a tiny Yorkie before:
Puppy Care and Puppy Info Library - YorkieTalk.com Forums - Yorkshire Terrier Community - there is so much on here about development and how to help your dog get through it, among many other things you'll need to know about Yorkie puppies.
http://www.yorkietalk.com/forums/pup...w-parents.html
Be sure you know all of the signs of hypoglycemia and how to treat it immediately in a dog this young. It can save a puppy's life. Some really tiny puppies are subject to hypoglycemia for up several months of age.
Dog Hypoglycemia (Low Blood Sugar): Symptoms, Treatment, and Prevention
I hope your enjoy YorkieTalk and your puppy!