It might be. It depends on the makeup of your body. For example have you had that in the past or is it new. It might also be a hyper sensitivity to the area. I remember everything felt different to me and I only had a lumpectomy with one lymph node removed. It took a while to feel normal again. Is it painful because edema usually is? Whatever it is you nurse navigator or radiation nurse might most easily help you figure it out. The nurses tend to be more sensitive to body changes than the doctors are, unless you have a very sensitive female doctor.