Hi Matilda54. I am also just over 3 weeks from mastectomy and have the same feeling solid and hard in my chest. My upper chest near the shoulder was more spongy and very tender. I also have a couple of hard cords going from the centre of my chest to my underarm. They make hanging out washing and reaching for the handheld shower difficult.
Otherwise my arm works as before.
The physio is working on the cords with massage, it isn't comfortable but not really painful, she gets me to talk about things which takes my mind off it while she works on the area.
She has shown me some massage techniques too that soothe the area.
I actually wondered if what I was feeling was ribs, it was so hard where the breast used to be.
I have another appt with the Physio on Thursday so will see what she thinks then.
My shoulder get really achey towards the end of the day too, it is my right arm and I am right handed, so it does a lot I guess.
I have a sleeve to wear, I haven't worn it yet.
Accepting these restrictions has me teetering on the edge of meltdown at the moment.