I've had this before, actually... been to the hospital for it once, even. It was during a cold when I was sneezing a bunch, so it really hurt my chest. The doctors looked at my heart reading (on the EKG thingamabob, I guess) and said that was fine, so it must be pneumonia. I left with antibiotics. I talked to my PCP the next day and got told "it's not pneumonia, just a pulled muscle, here's some aspirin++," and "stop taking the antibiotics, you've only had one of them so far so it's not dangerous to stop the course."
So... Um... What was my point again? Oh yeah, I seem to be fine. And thanks :)