<s>[INST] I have been feeling very sore in my lower left ribcage under my breast.  I have checked for bruising since its tender, but there is nothing on the surface of my skin.  I noticed yesterday that there is a horizontal hump/bump from under my left breast to the sore area of my ribs.  What could this be? [/INST] Hi, dairy have gone through your question. I can understand your concern.  You may have breast lump, muscular pain or rib cage problem.  You should go for x-ray and mammography.  It will clear all doubts.  If it is breast lump then go for biopsy. It will give you exact diagnosis. Then you should take treatment accordingly.  If it is muscle spasms or pain then take muscle relaxant.  Consult your doctor and take treatment accordingly. Hope I have answered your question, if you have doubt then I will be happy to answer. Thanks for using Chat Doctor. Wish you a very good health. </s>