Pain in left side of chest when breathing?

So I'm pretty much a physical wreck lately. I'm generally pretty active. I'm 18, and I smoke. Once in awhile I get a pain in the left side of my chest, kinda under my collarbone but almost under my armpit. Its only when I breath. Both inhale and exhale, sometimes worse then others. Also, to add... I discovered today I have a hard lump on the back of my head, kinda on my neck.. On my left side, but nothing on my right side.. Doesn't hurt, just strange.