Radiation to the chest wall is certainly associated with the risk of some long-term complications, including necrosis (death) of the bone, fractures of radiation-damaged bones, accelerated arthritis, and, in rare cases, the delayed onset of cancers of the bone, cartilage, or fibrous tissues (sarcomas).
You did not indicate when you underwent these radiation treatments, but your symptoms merit further work-up, in my opinion. (One must also always be alert to the possibility of recurrence of your breast cancer.)
Sincerely/ Robert A. Wascher, MD, FCS
http://doctorwascher.com