@arpie the sore rubbed feeling armpit could be neuropathy which is caused by them having to move around the major nerves when they do the axillary dissection. I had it really badly with the wide excision and it's still there a little from the mastectomy. I found that putting padding through the side of my bra and tucking it over the top helped a bit. Or you can use some of that paper tape and tape some padding across the sore part. There doesn't seem to be much you can do about it - just wait for the nerves to sort themselves out.