Sounds a lot like the lump i've found on mine. Same finger same joint.
I was reliably informed this xmas, by the family physio (gf's sister - free physio
), that it is caused by ligament damage.
The lump itself is 'soft bone' which the body produces in response to the aggravated ligament.
If you feel pain, or hear/feel a click at the joint when you try and bend it sideways, this is the most likely diagnosis.
The ligament damage is caused by lateral movement or loading of the joint. When you crimp, that finger 'rolls' over towards the other fingers, crushing the inside joint. So try not to full, or even half-crimp on it.
I was shown a method of taping with a strip running up either side of the finger and then bands either side of the joint to hold them in place.
It seems pretty ineffective in terms of support really, but i've been doing it anyway.
Was also instructed to ice it after climbing to lessen any swelling and prevent further build up of soft bone.
The soft bone already produced will reduce once the inital injury is cured.
And last but not least - rest it.
Of course, i'm not a physio myself, so take the usual kilo or two of salt with this diagnosis and go see a real one.