Cyst on finger

Hello all,

I went to urgent care yesterday because the pain in my fingers was so bad and during a physical examination, the doctor found what appears to be some kind of fluid-filled white cyst on the backside of my pinky? We did an ultrasound and I’m waiting on the results. She brought up RA as a possible cause for these, but has anyone with PA developed any as well?

https://imgur.com/a/L8YhQ1e