What Causes A "pop" In The Palm With Pain On Pressure?

I was writing the other day. As I was holding the paper (with my left hand) I felt a pop at the lowest point in my palm. It's in the center and while it doesn't 'hurt' all the time, I can feel it and if I do certain movements or put a little bit more pressure on it (when erasing or something) it hurts again. Is this something to be concerned about?