Well I know you shouldn't put your puppy on the ground outside until he has all his shots because you run the risk of him getting parvo and it could be deadly. I don't want to scare you, but you should know how serious it is. About him biting, I got my Bella at 8wks and I was told that yorkies shouldn't leave their moms and siblings until they were at least 12wks old. Reason being is that between the ages of 8 and 12wks is when they learn how to socialize with others. Ex, if they bit too hard while playing with their mom she could correct him the dog way. There are so many posts regarding what to do about this, Yt is great!
I will just give a little exagerated yelp, to show her she has hurt me, and then no longer play with her, kinda ignore her. She gets the point, now, and then she will come over and give me sweet kisses. Every yorkie is different so just see what works for you. Good luck!