I had terrible cording after my SNB and then my ANC/mx. The pain can be horrible and gradually creeps down your arm. Exercises were so sore.
I had to have some Physio where she gently applied pressure to the cords in my arm starting at the lowest point and working up. She told me to do the same. Sort of gentle circular movements with firm still pressure to finish. It hurts but it does get better over time. Just remember to work from wrist upwards to help with any fluid buildup from the massage.
I also had a lot of scar tissue and the cords seemed to be trapped in amongst the lumps under my arm. For this she told me to massage the area firmly throughout the day. So I used to press under my arm when I was watching telly, making tea, reading, in the shower, etc. after a few days I felt the scar tissue kind of tear when I rolled over in bed! Bit of pain then relief and movement returned. Took about 3 months to really feel better both times I had it.
Sorry if this is a bit detailed but having had it twice, I feel something of an expert! Good luck and do insist on getting Physio if you find it getting worse or restricting your movement. It really helped me.