Sounds like nerve damage. I'm no doctor, but I've done some nerve damage to my arm before. From what I know, there are 2 major nerves running down your arm. One connects to your thumb, forefinger and middle finger. The other one connects to the last 2 fingers. I believe the one that connects to the thumb, fore and middle fingers also runs along the palm of your hand, so you could have nailed that one braking hard.

Do you have any tingling in any of those groups of fingers? I did damage to the one that controls the first group and it made my entire arm weak - I couldn't even do a pushup against the wall, so it could be the same thing.

Good luck and I recommend seeing a doctor/physiotherapist to help speed the healing.