I'm sorry to hear about your difficulties playing.

I have chronic pain in my hands, not helped by having to type to make a living (but not too bad for the past few days, fortunately). It was worse when I was only playing the guitar, but I've found that it helps a lot to spread the strain around by playing other instruments.

A couple of weeks ago I had some bad pain in my right wrist and couldn't figure out where it had come from. Then, I picked up my alto recorder and played something involving the low notes and thought "That's it!" It's gradually disappeared.

A chromatic harmonica is a very versatile instrument and I'd like to add my voice to those recommending it. Learning to find the notes on it reliably (especially skips) is a challenge that keeps practicing interesting.

I hope you're able to keep playing.