@jenott thats a good question.
I had 25 rounds of rads
I get what feels like a stitch just under my treated breast still get them. I always put it down to moving the wrong way or having done too much lifting or stretching up, I can usually massage it away. Now though I’ve been getting it on both sides Its not debilitating but annoying and painful. at one stage I had an uncertain area come up on a ct near my sternum and as it was tender and it could be felt. biopsy was ordered by Oncologist. Turned out to be scar tissue the Radiologist took quite a lot of it out in the biopsy as it had penetrated my chest wall. After that the bulk of the pain has gone from that area just get twinges every now and then as there is still scar tissue in there. The other thing he biopsied was my calcifying seroma which never dissolved. Nothing has shown up in the chest area where I get the twinges
I think with everything we’ve gone through we tend to be more concerned about our bodies. For me I prefer to ask & get whatever it is checked out. If I hadn’t mentioned back ache and leg pain My Mets would have been missed it was picked up early as it was it just happens it started pressing on my sciatic nerve. Nothing showed on xray it was picked up with CT and Pet scan and the blood test showed my markers started going up
this of course is what has happened to me and not necessarily what could be causing your pains
Better to find out for sure then be left to worry. Hope you find an answer to what is causing your issue.