Hi, My left side has been sore for days. It feels like it is my rib cage, but I have noticed that running my hand up underneath my left breast is also incredibly sore. Tonight when I was trying to locate where the pain was coming from, I discovered what was like a cord-like, vein-like thing under my left breast . I can almost follow it down from under my left breast to where it hurts in my rib cage. Is this something that needs immediate medical attention. I am 30, female. Thank you.