I had lumpectomy May 2024 and breast reduction at the same time, also surgeon removed 4 lymph nodes. I’ve been pretty sore also right side of breast and arm pit for months now. I saw my oncologist 3 1/2 months ago, she said I had lymphedema and she sent me to occupational therapy. The therapist has found cords in the arm pit that go down to my wrist and she suspects to the breast. Cords can develop after surgery. So, I’m wearing compression bra again, a compression sleeve on my arm, massaging under the arm and side of breast and doing different stretches that hopefully will help. I guess when they remove lymph nodes, that can cause fluid to build up where the lymph nodes are no longer there, causing pain. Maybe check with your oncologist to see if this may be the cause of your pain.
I wish you the best!

My right side close to the underarm never fully
Closed from my bilateral mastectomy on Apr 1st and has been very sore the whole Time. So with the sentinel node biopsy today, they reopened the same spot and fixed a few issues while taking the nodes so I'm hopeful that I'll heal better this time (been sore for 2 months).

I had a bilateral mastectomy and two sentinal lymph nodes from near the arm pit area on both sides were removed. The sentinal incision and the area are around it stayed sore and tender much longer than any other surgical area. Like months longer on both sides. The other surgical scars also healed faster than the lymph node incision scars.