I know it's probably late to answer, I guess you're talking about the obliques? You might have gotten oblique strain, probably by overstretching the muscle. If it still hurts you, you should probably ice it, don't irritate them even more, but there's a high chance that the pain is gone till now, or will be gone in a few days, if it doesn't go away in a few days, take a break. And next time, make sure you also warm up your torso, by oblique stretches (google it) and a few other warm up exercises. I hope it's nothing serious, and it probably isn't.