Glad it didn't turn out to be anything really serious.

If you haven't heard of it before, look up costochondritis: it's an inflammation around the sternum and ribs around the center of your chest, usually from having your arms and shoulders pulled forward for longs periods of time, i.e. working on the computer all day. It depends on the kind of pain you're having, but there's a lot you can do to relax the muscles and hopefully get the pain to subside, if that is indeed the case.

Hope you feel better soon!