HiJoleystub likewise I have had cording (mild compared to yours) initially under the armpit and then down the side of my ribs.
My surgery was 24 months ago.
The cording and range of movement improved after seeing a bc specialist physio but I still have sensitivity in that area. In addition to practicing the stretches I was given the physio also used a laser.
I do yoga and find that the stretching and twisting really helps.
I take Letrozole and I think my feet and ankles are more affected by this (they get stiff and especially at night feel achey.
Wishing you relief soon!!