Hard, movable spot on the tailbone. Is this serious?

Hello folks,

For a few weeks now, I've been having slight discomfort when I sit when pressure is applied to my tailbone. Two days ago, the pain got a bit worse (still not that bad), and now when I touch my tailbone, I notice that it's hard and has a movable part there (feels like cartilage, somehow). It also hurts when I press on it a bit. Now I'm not sure whether I should go to the doctor about it, or whether it will go away on its own. When I asked chatgpt, he said it sounds like a tailbone fistula. Could that be it? Should I see a doctor? Can I call 116117 and ask whether I should see a doctor about it?

Thank you very much 🙂