Oil pump light stays on after bike fell over in driveway

Check your oil level and antifreeze level or change your oil if the problem continues

I don't like the sound of that on two counts. The oil pressure warning lamp should come on only when the engine is not running and stay on until the engine is running, whether in or out of gear.
The metal slapping sound is possibly, due to the cold weather depending upon the high mileage, piston slap. That is not too serious in the case of an Iron Head, (like my 1963 XLCH1000) as they have done many miles but a newer machine it is somewhat worrying.
A good friend of mine has a 1200 Sportster. His problem was oil pump. The pump couldn't keep up with the engine revs and he finished up on one piston, the other was in the sump.

Make sure the oil pressure is good and check for dirty oil. If the bike has not been started for a while, the dry sump fills up with oil and that causes odd noises until it clears ina minute or so.
Check that oil warning lamp!!!

First of all , change your oil pressure sender . It should be easy to do and relatively inexpensive. See if that fixes the oil light going on and off. If the light stays on after that , turn off the bike and replace the oil pump. If you have a bad oil pump and continued to drive the bike , you may have caused serious damage to the motor and may end up having to disassemble the engine to determine the cause of the knock.

Dont drive it until you know the problem. Unless you are rally brave, if it really has no pressure it will destroy the engine

check or replace the oil pressure sender switch , and the relay( if it is the oil sender relay)

the light will stay on until it gets oil pressure ie: when it starts, there is no oil cutoff switch

check for a broken wire on the side you droped it

Oil light does not mean that you don't have oil inside.It means that there is NO pressure in the oil circuit.You should check your oil pump and hope it did not ruin your engine from lack of oil underneath the pistons.Measure the compression too.

You will need to get a mechanical gauge to check for sure, but it sounds like your oil pump is not pumping enough pressure, or you have a big clearance somewhere in your motor that you are losing pressure at.

yes they can and no i wouldnt drive it