Bad luck on the trigger finger and arthritis - I know the feeling!
A few years ago, I got 'trigger finger' in the thumb of my fretting hand. This seemed like the 'final nail in the coffin' of my guitar playing, as I'd had a few years of very painful arthritis in my fingers - to the extent that I lost all movement in the first finger on my picking (right) hand. I'd already started to learn to finger-pick using my thumb, middle finger and ring finger - no way I could hold a plectrum. That was hard but beginning to pay off, then I get trigger finger in my thumb. Apart from the pain, it was impossible for me to hold a chord down. Somehow, the inability to hold the neck in position (without using my thumb) made playing a non-starter.
Long story short, I went to the doctor and he said rest it for up to a month - no guitar playing - it should cure itself. And it did!
I know people who have had cortisone injections and they have helped them to continue playing but, for now, I've avoided that particular route.
So, my advice is that you give your trigger finger time to correct itself, and, once that's done, if you can, try to find ways around the arthritis problem by altering your playing style. It may not be possible, I understand that, but guitar playing is too good to give up without a fight, so persevere!
BTW, I can now finger pick as well as I used to before the onset of arthritis - that ain't saying much, but it's really rewarding.
Good luck with your struggle!
