Hi @Chev
Didn't the hospital book you in for physio follow up? I had lumpectomy and level 2 axillary dissection. The cording started about 3 weeks after surgery. Under my arm pit and down to my elbow. You could see the guitar string inside my elbow, gross. Nasty stuff. I had 3 lots of physio at the hospital (supposed to have 6 but oops bad patient) and that's about all it took. I did do twice the amount of recommended exercises and a lot of massage and stretching myself. Lots of the wall walk.
It hurt like heck at the start though so take it easy first up. It made me feel quite nauseous the first week or so.