Relax! I'm sure it's no problem.. you probably just aggravated a tendon or something. Take anti-inflammatories and rest it. Those types of things take a little while to heal because of the amount you use your hands and arms.
If it's not better in a couple of days, go get it checked out by a doctor.
I'm sure your fine.. I get little aches and pains every now and then from playing. Once the outsides of my wrists hurt so bad that I couldn't even play.. I had to stop for a few weeks. But I'm all good now. And have been fine every since.
Usually, it's because you are playing with too much tension in your hands. Seems obvious, but I didn't realize it until I was in my mid twenties or so. So, make sure you're not straining too much. It's an easy thing to tell by video recording yourself while you are playing.
Don't worry... you'll live!
