In reply to Anonymous:
Have you tried strapping it when you climb? 25mm elastoplast fabric strapping is a good size for fingers. About £3 for 4.5m from Boots.
Wrap the finger in tape starting 5mm from the nail. Overlap each turn by about 5mm. The tape should go right to left across your finger. When you reach the back of your hand, continue the tape down towards and under your tumb, and then across your wrist right to left. Finish off by taking the tape up the back of your hand so that it crosses itself. When you wrap your finger, you want it to be in a natural resting position, i.e. slightly curved.
The tape is reasonably stretchy so you can move your fingers, and quite grippy so you don't lose too much friction on the rock.
There are lots of other strapping techniques for supporting fingers, so speak to a sports physio about it.
P.S. If you strap fingers on your left hand, all the tape should go left to right.