As far as arthritis goes, movement is definitely recommanded generally speaking (except in crisis state where you need to pause completely). It seems to me that starting to play while discovering your arthritis, is a happy coincidence. Now as you are new to the game, you might want to stay aware of the tension while playing, position, playing duration... Because while learning you might not be 100% into those things. To be fair, even seasoned players continue to learn on that, not counting the constant adaptation to body changes due to aging... *whispers*
Also, in early stages of learning, you may "push" a little bit yourself sometimes, because you want to be doing certain things, because being passionate and all. Like a sport : it could be a good idea to have some kind of reasonable and tailor-made program, applied regilarily, so you can have a safe and consistent physical reinforcement and learning curve, without hurting yourself. Pushing, yes, but reasonably and regularly.
I'm saying this because i did the opposite many times in my life, i probably check all the wrong boxes, and now that i (re)starting to learn singing from the ground up applying this, i can appreciate progress and how i don't hurt myself doing things, for a change ^^ I think it applies to everything. I mean especially with things you love, it is easy to overdo... Playing hours in bad body positions and tension because you want to "get there", you know. And not playing at all the rest of the week because, you got "no time"... Better playing a smaller defined and efficient time, every day if that is possible, push things but not too much, and leave things to the next day to go further. Regarding our body use, even for arts, it is very similar to sports, there is physical awareness needed.
My two cents ^^