pulled muscle in ribs/abs area

I have had what feels like a pulled muscle for a couple of weeks now, on and off....on now. It is just below, almost attached to my ribcage on my right hand side, and is okay most of the time, but hurts pretty badly as a result of certain inconsistent regular movements just around the house. While training, it generally does not seem to bother me much at all. Though yesterday I attempted my first sprint tri and while attempting the run, going from walking to running, it hurt a bit, but only when starting to run.

It does not bother me while sitting etc...I am not sure what to do...take a few days off? When it does kick in it hurts pretty badly, almost takes my breath away, so is pretty annoying!

Any thoughts???