The radiation would have damaged cells, hopefully most of them were cancer cells. There IS no radiation now, although maybe the cells may not reproduce like they used to. Hell, a lot of things I have, including mosquito bites, don't heal anywhere near as fast as they used to.

It really does sound more like an ingrown hair or a cyst with something stuck in it than anything else. Also, just because I talked about mosquito bites up there, is there any chance it's an insect/arachnid bite/sting? Not all of them will cause itching.