Most likely constipation, or inflamation from something you ate. Try to go number 2, take some ibphrofen, and you should be alright.
If you are female, and the pain is Very low, it could just be a regular cyst on your ovary which is also very common and normal.
Give it a few days, and if it doesn't clear on it's on after that then see your doctor, but that area has no need for alarm.
=)
