Odd Rib Pain On Left Side

Hi There,

Recently (Over the past couple of days), I've been experiencing and area of mild soreness in my left rib area, a few centimeters below my pectoral and slightly above the bottom of the sternum.  If feels as if there is a muscle knot and the pain appears to continue slightly into my armpit, but not at all onto my back.  I DO NOT have any other symptoms such as difficulty breathing, fever, etc.

Also for the past couple of weeks, I've started a 4-5 day work out regimen, but haven't received any trauma to the area.  I also generally sleep on the side where the pain is localized.  I'm 33 years old, healthy, non-smoker, and generally share a bottle of wine with my girlfriend every night.

The soreness has only been there for a few days and I'm just wondering - if the pain endures - if it could be an indication of anything serious.  I'm planning to get checked out by a doctor, but just thought I'd ask, as internet symptom sites can be a little scary ;-)

Thanks!