Last night while playing with my daughter and husband, Max landed wrong and immediately started yelping and holding his foot up. I ran over to him to see what happened. The joint on his front right paw (on the inside where his ankle is?) is swollen and he is limping badly. He will let me touch it and move it without showing any discomfort. By the end of the evening he would put a little weight on it occassionally, but this morning he is still favoring it. He is still eating, playing, etc. Is it sprained or could it be something worse?