I've had a similar injury just prior to fight time. You are already doing the most important thing, which is going to see a doc to rule out anything dangerous or fractured. If it is just muscular, then you have to ask yourself these basic questions, does it affect my breathing and will I be able to withstand the pain? In my case adrenaline took over at fight time and was like it never existed until about a day after the fight. And then it hurt like a sunnamabitch for a few more weeks and lingered longer. But you can rest then so healing gets a lot easier.