What Causes Shooting Pain On Top Of Hand?

I have a shooting pain in the top of my right hand. It is right in the middle and it feels bruised but it is not swollen and there is no discoloration. This happened to me once before and the only common event that I can think of would be using weights at the gym. (I am a small girl *125lbs*, the weights are only 15 lb dumbbells!) My questions are: A-What could this be? B-How can I prevent this from recurring in the future? It hurts any time I use my hand for something or move it using a wide range of motion.