Can A Lump Under The Right Breast Be Treated?

I am a 68 r old female, active/contractor/builder and recently I noticed a sore spot located underneath my right breast against the curve of the rib cage that as a small pea sized lump. The area stays quite sore ot only to the touch, but with movement is mildly painful. I am a colorectal cancer survivor w/APR and permanent colostomy, and was on a 2yr /every 6 mos breast watch on the right side as well for a small area located in the areola that was recently reduced to every year. I do occasionally do things that could cause a strain, i.e lifting 5 gal paint buckets, etc. Any idea what is going on? I am in Canada right now, but docs are in Florida.