OW! Oh, I know how badly that hurts. I recently broke my finger by slamming it in a car door(embarassing).
Keep your hand elevated and do an icepack, to reduce swelling. A bag of frozen peas or corn is perfect for this. & Try to keep your hand elevated for a few days, as much as possible. There are splints that you can buy at any pharmacy to keep the area protected while the swelling/pain persists. Do not use these splints all day, however, and not for an extended period of time. Immobilization impedes circulation & you need good circulation to heal... :D