Apologies for the gruesome photo of a rather manky finger.
My finger swelled up over night and is incredibly painful to the touch. A doctor friend of ours tells me that it is paronychia, a bacterial infection that gets under the cuticle, and it has now started to track up my arm, so I have got antibiotics to head it off.
As an aside, it is apparently impossible to take a photo with a modern SLR with just your left hand. They are so completely ergonomically designed for your right hand that you simply cannot hold them and release the shutter with your left hand.