knuckle injury?

disclaimer - i am not really seeking medical advice per se, just opinions on when i should go to the expensive dr. also i apologize for the typing, reason will be clear soon.

ok, so i woke up sat morning with a knuckle in my left hand very swollen and painful. it is one of the knuckles that is right by the hand not out on a finger. i went to my reg dr and he said he doesn’t think it is an injury or infection and gave me prednisone which worked the first day and that’s it. now he says i should see my rheumatologist, but that costs 50 dollars i don’t want to spend for no reason.

so, question - is it possible for something other than an injury to suddenly show up like this? oh, forgot, it’s not gout, he ruled that out. i can’t just call the rhuem dr and ask because she won’t do phone consults, gotta go in. i don’t remember doing anything to this hand that might cause this but maybe i did?

help!?