It is difficult for me to comment, given the limited information that you have provided, and my inability to examine you.
Certainly, patients can develop areas of edema (swelling of the skin) in the breast following breast cancer surgery and radiation treatment. Also, most patients who undergo radiation therapy for breast cancer will develop areas of skin "tanning" (hyperpigmentation) where the radiation beam passed through the skin.
If your surgeon is concerned about the appearance of this area, and there is any suspicion that it might be related to your prior breast cancer (or a new breast cancer), then a small punch biopsy of the skin in this area can be performed as an outpatient.
Sincerely/ Robert A. Wascher, MD, FACS
http://doctorwascher.com