Focal dystonia is horrible and recovery is very slow if it ever happens. The pianist Leon Fleisher is the only musician I know of who ever got over it - after about 40 years. The bagpiper Hamish Moore has it, and he has adapted by using his right pinkie for what his ring finger used to do. Looks bizarre but it works.

It's basically caused by the brain rewiring itself in a counterproductive way.

There was a useful series of articles about ut in Piping Times, under the title "Losing It".