Sore Finger that won't heal.?

I race motocross, and I was practicing about a month ago. My hand slipped off the throttle grip, but didn't come completely off and my pinky finger being the shortest I think I hyperextended it because itwon't stop hurting while I'm riding since now. It's really affecting my performance and I've tried to ride through the pain but I can only go so fast when I can barely hang on. I've been to my Dr. He said he couldn't find anything wrong and he's been my Dr my whole life so I trust him. I've tried icing it, the hot rice in a sock thing. STILL no improvement. I really need some suggestions. SOMEBODY HELP