That really is a bummer. Ive been fortunate enough to not have any serious issues from playing. Callouses and maybe a sore finger nail corner.
There was something a pro wrestler said one time that stuck with me about long term or serious injuries which he never ended up with after a long career performing. He basically said that he never performed anything he couldnt do and stayed within his limits.
I tend to apply this to my bass playing. I have my limits in hand size and technique and really try to stick with it even at the sake of some jeering.
Small hands, sissy pinky = short scale bass, 1-2-3 fret fingering.
I am absolutely not saying you have to do this. I am saying a technique change, a lighter gauge flat, and a better outlook on your hands and fingers. The shark cartilage supplement, a stretch routine, icing when pain first occurs etc...
I would hate to have to lose flats or not be able to play at all. But a little more care and understanding of your ability and biology will probably be something you may need to take hod of for the rest of your life/bass days.
California Bassist #98/Fresno Area Bassist #9/Ibanez Club #1131/SX Bass Club/Squier Owner's Club/Squier Jaguar SS #76/Short Scale Club #360