If you laid off the thumb and it still hurts, you could've torn the ligament, then you should see a doctor, but a sprain can last a long time if you keep using the muscles around it. Sprains hurt worse than breaks for the most part (I've had both many times). Splint your hand (basically not use it at all) for two weeks. Use a popsicle stick to keep your thumb stationary and another for your forefinger, then half up your hand towards your middle finger. wrap your hand (not tight, but not loose) with an Ace bandage. Take it off at night (DO NOT SLEEP WITH IT ON).
If your future depends on your hand, see a doctor, I am only saying how I delt with brocken fingers and thumbs, I draw and have been fine.
You SHOULD REALLY SEE A DOCTOR if You Question your injury.