Well, I just got an opinion from my mom (who is a certified medical something or another. Basically, close to being a medic without formal schooling).

She says that it's probably just a passing pain in my lung. She doesn't know how it would happen, but I don't think I'll die in the night, so I'll ask her again in the morning.

I asked these boards because I know there's a psychiatrist (smellie hippy, I think), and was hoping that there was other people that were similar, except experts in the body rather than mind.