Don't worry, it's not a health problem, he's probably a parti
Here's a few threads: Read the third one first
How much white makes a parti? What is a Parti Yorkie http://www.yorkietalk.com/forums/gen...formation.html
P.S. - Plus side about white toenails - they're easier to see where you have to trim
Post a pic when you can, I'll bet he's really cute