bizarre - discolouration under arm again

As I was walking into yoga tonight, I felt sore under my left arm and possibly the armpit too, as if the skin was chafing. During the class was aware of it but not a big deal. By the time I got home, it was damn sore again so pulled up my t-shirt and said to The Yoga Man: "it's sore here; is there anything there?" It looks bruised," he said, "even below your bra."
Well, went to inspect it in the mirror and low and behold, the skin is discoloured again. A bit bigger area than had been discoloured from the radiation before, but less intense.
It is how many months since I finished radiation - maybe about four or even five - and now this deterioration. Only yesterday The Lymph Lady had said that one's skin can take up to seven years to change after radiation.
Well, I will be at the oncology centre on Monday for my three weekly dose of herceptin so will ask them then. Bizarre.. or is it?