You could be suffering from cording…
What is Cording?
Axillary web syndrome (AWS), also known as cording, sometimes develops as a side effect of sentinel lymph node biopsy (SLNB) or axillary lymph node dissection (ALND)
The cords tend to be painful and tight, making it difficult for you to lift your arm any higher than your shoulder or extend the elbow fully. This pain and limited range of motion can have a major impact on your day-to-day life. Cording can be especially problematic if it happens before or during radiation therapy, since this therapy typically requires lifting your arm above your head.