I just went through this with Mikki. She does have LP. She jumped down while playing and was limping. She too would not put weight on it either. I made her rest for a few days and did not allow any jumping at all. I totally understand how you feel. I was in tears! She ended up being completely fine after resting. Here is the post and advice I got.
http://www.yorkietalk.com/forums/sic...t-her-leg.html. I hope rest will do the trick for you too. I would take him in if he isn't better tomorrow. Hope your little guy feels better soon. Please keep us updated.