Soccer ball to the chest – should I be worried?

My 15-yr. old daughter was hit pretty hard in the chest with a soccer ball during a game on Sunday. Sunday night she mentioned in passing that her chest hurt. I figured, sure it hurts – she was hit pretty hard and is probably bruised. By Monday night she said it hurt to breath, and this morning (Tuesday), she’s walking a little hunched over and complaining a lot. I called the doctor, and they can’t get her in until Wednesday afternoon (tomorrow). I’m surprised they didn’t feel it was necessary for her to be seen right away, since she’s having trouble breathing because it hurts.

I don’t know if this is normal, or if I should head on over to the ER.