You could also be dehydrated or may have over done it today. Up your fluid intake and lay down for a bit and rest. It should ease up. If it continues I would notify your dr just in case its the start of a uti. Getting those treated quickly during pregnancy is important because untreated utis can cause preterm labor. If it gets worse or you have any spotting visit the er. And the other poster is right, some cramping here and there is normal and it could be nothing but I am always overly cautious. Better safe than sorry. Good luck.
Light cramping is normal. Your baby is still growing like a weed :-).