If your son just cracked the pan, you should be ok.
Having dinged my own sump last year

...I know from experiance that it takes quite some time before you run out off oil.
First you will get an oil level warning with an audiable "ding" before your oil pressure light comes on...followed some time later by several non OEM audiable warnings from under the hood.
I would replace the sump a.s.a.p. and not turn the engine over if possible.
some tiny metal parts might be lurking in the sump waiting to be sucked in.
Oh and if you get a "breaker" sump instead of a new one... be very sure to wash out and clean the pan thouroughly.
My replacement apperently came from a M5 that had shedd its bearings.....you wont believe how much sludge and metal cam out of that pan...
While you have the pan off, check all bearings and bearing bolts and check the pump off course.
Could be just a bad sensor.
greetz
Tamar