I am a 24-year-old male, who hardly does any exercise but is generally in good health. I played one game of tennis one month ago. Afterwards I was pretty sore and stiff all over, but was fine after a few days, except for my wrist; I have had a small amount of pain in my wrist at the bottom of my thumb, where it meets the wrist on the palm side which I thought would eventually go away, but is still there now. It doesn't hurt much except when I move it in particular ways, e.g., if I bend my wrist forward the whole way, and even then the pain is not too much. I have a slight lump in that area as well (more than on the other hand). I play the piano for a living and it does not really seem to have affected my playing, but that is the reason I am concerned about this; otherwise I would not worry much about it. I have been busy playing the piano quite a lot since the tennis game.
What do you think is the problem with my wrist, and how can I fix it?