I backed over a large rock this Morning and it.

Hello - do a real good visual inspection inside and out. If the car is not cracked like you said and no water can get in from the bottom and it isn't affecting the performance of the car or the storage of the tire you should be fine. Make sure no cables or lines were damaged, as long as it is just the sheet metal again, you should be okay. If you are still worried then stop by a body shop for their visual inspection.