Hi ~ Sorry to hear about your baby. You should really try to get him to a vet sooner than that. If it is anything serious and it is not seen by a vet it will get a lot worse very quickly. I understand about lack of funds but if he does need surgery and cannot afford it there are wonderful rescue organizations that can help. United Yorkie Rescue is one of the better known and I believe they help throughout the US.
I cannot stress enough that your baby should be seen immediately. Permanent damage can sometimes be done when we wait and see. He may have a sprain or it may be something more serious. In the meantime I wouldn't play rough and try to keep the jumping off of things to a minimum if possible ~ he is a yorkie after all!
Keep me posted ~ positive thoughts that everything works out...♥