Definitely get it checked out.
I finished radiation 4 months ago (30 rounds) and my breast was a tad smaller than the other with a dent, where the tumour was removed. It now looks about the same size as the non radiated breast and the dent is not visible any more.
My radiated breast was a lot harder than the other one and the pain was intense especially the nipple.
I did get it checked out by BC nurse, GP, Surgeon and oncololgist - anyone I visited as I was really worried about it, they all said normal.
The good news is the pain is gradually getting less. I guess everyone's body reacts in different ways.
Good luck and I hope everything settles down soon. xx