I had vulvectomy in January, with 28 radiation treatments. I finished in April and recovered well, then in late June I started to have severe pain in radiation area, top of legs, groin, etc. My radiation oncologist suspected scar tissue had formed, so he sent me for physical therapy, to break up the scar tissue and work the muscles. Radiation not only affected cancer area, it affected all the good tissue too, the muscles, tendons and such. I will tell you that it was painful at first, but I have regained range of motion back, and pain has lessened about 80%, I still must work on scar tissue myself, with massage, and I am still in treament, but near the end.
I would definitley talk to rad/onco again, and ask about this issue, you should not have to suffer. It is also possible to develope an infection, so it is in your best interest to pursue this until you feel satisfied, you should not live with pain and possible disability.
I wish you the best, hope you are doing well and recover from this awful disease quickly.