If in doubt, get checked out, @Mousie. The warmth following radiation often lessens over a few months. But individuals may vary.
My affected boob was (unbeknown to me) was significantly larger than the unaffected boob - so by the time the lumpectomy was done, both are now roughly the same size! Amazing that in my 65 years (when the lump was dectected) I had never noticed!!
I still get the occasional 'stab' of pain (similar to what I had during radiation) and the same with tenderness. If any of these symptoms persist - get checked out.
All the best xx