I found a pea-sized lump on my right ankle that appeared about 1.5 mo ago. it's firm, not painful, hasn't changed in size. should i be concerned?

Likely benign: Most commonly these lumps are ganglion cysts which are benign fluid filled sacks that come off a tendon or joint. If u have a little flashlight then put it against the bump with the lights out and if the bump lights out it is a cyst. Nothing needs to be done unless it rubs on shoes or causes some other orientation. However if it enlarges, becomes painful or red, you should see a specialist.

Lump: Did you have it removed the first time and biopsy. If not that should be a consideration.