Thanks for writing in. You have not mentioned about the details of your breast cancer treatment
(like size of tumor
, grade, receptor status, node positivity, etc). These are required to understand the risks of it coming back.
The possibilities of this kind of pain may be infection in the throat, muscular or skeletal pain unrelated to cancer, or spread of breast cancer to bones or pleura (in the chest).
You certainly need a physical examination and may be a few tests to diagnose the exact condition.