In reply to mikekeswick:
I've been plagued for years by these. My usual matra is rest and massage (firmly, along the length of the finger). And wait until you're absolutely sure it's better - an experimental pull-up will put it back to square one. It is not possible to 'climb without using it'. Tape it up when you do start again - Strappal is the only tape worth using - the others either don't stick or have some stretch, which renders it uselss for supporting a pulley.
However, we were having a clear-out recently and I found a pair of those Chinese ringing balls (shiny metal things that go 'clong' and vibrate when they're knocked together (sub-snooker ball size). Heaven knows where they came from.
I thought I'd give them a go and found that the gentle exercise and the vibration worked a treat. It's even better when they're cold.
Highly recommended.