I cannot stress strongly enough the need to get finger and thumb problems evaluated by competent medical people.
I went with a somewhat skittish friend who was going to have finger joint pain evaluated, and as expected, they sent us for an X-ray.
When the film was ready, the radiologist (not a technician) brought it out, and asked, "who are you taking this film back to?" It was clear from their body-language that if it was a general practitioner, we were not getting the film.
We answered, "Hand specialist and plastic surgeon."
"Oh, OK here you go."
When the hand specialist put the film on the light to display, they said, "Oh, an enchondroma. You will need to have surgery to get that out. Otherwise it will take over the bone, envelop the adjacent joint and turn it all to mush. By next year there will not be enough left to fix."
Enchondroma is a typeof benign bone tumor belonging to the group of cartilage tumors
https://en.wikipedia.org/wiki/Enchondroma