Pain after mastectomy/stage one reconstruction

Hi there
i am now in my third week of 5 weeks of radiotherapy and the left breast which had the mastectomy/ tissue expanders had settled down a bit before I started but now it is hot and inflamed a couple of hours after each session ( skin still holding out well as I am using Strata X ointment).
Anyone else experienced this?
My radiation oncologist said “ this sometimes happens” and prescribed me some more Endone.
which I am taking as required.