Radiation over and now my breast is so sore is this common?

It is completely normal.  The SE's of radiation continue for up to two weeks after treatment finishes and for me, the week following the end of my treatment was by far the worst.  At one week post radiation, just when I was about to scream, my skin started to heal and recover very quickly.  Hang in there.  IT may get worse before it starts to get better, but soon you will be healing and rads will become a dim memory.  Four months later and I seldom even think about it anymore.  ((((hugs))))

Call your Rads Dr!  No one here can tell you what is going on with you.  We are not medical staff who actually see you.

I had no skin issues until the morning after last rad,  when the entire irradiated area was 'open' and only got worse.  That was early March and the last scab came off on June 29.

Call your Rad Dr (not Chemo Dr).