My left arm has a tingling pain?

About four days ago, I fell off my bike pretty hard, and slammed my left hand onto the concrete. My palm hurt for the next couple of days, but not my entire arm. All of a sudden, I woke up and my entire arm is very sensitive, and it tingles with slight pain when I put pressure on the skin or even when the arm touches something cold. I'm not sure whats going on, but I think it may have something to do with my fall. my arm also feels very weak. Any ideas?