Check engine light on; oil gauge is low-none when idling.

If you hear no ticking or knocking from the engine , likely the condition isn't serious yet. But, it needs to be checked out immediately before it does.
I would either replace the oil pressure sending unit or have a mechanical gauge (yours is electro-mechanical) temporarily installed to read the actual pressure. If it is in fact low you need to find the cause and correct it.
Oil pumps rarely fail but the pickup screen on the pump can become obstructed, bearings (both crank and rod) often wear,and most times rod bearing change will help. Your actual oil pressure should be about 40 running warm and about 60 cold. On some engines you can "get away with" pressures as low as 15psi but no manufacturer builds them to run at those low numbers.If oil pressure was not that critical, race engine builders would not make any effort to boost it, as higher pressure pumps steal horsepower, yet many race engines run pressures in the 150-200psi range.(you can't do that or your filter would explode).
Chances are, you only need a sending unit replacement, but don't ignore the problem as it's cheaper to do the repair now than to replace the engine.
Good luck!

Can be a numerous issue with service engine light, the best way to narrow it down is stop by auto zone and plug it to the computer and see what code it spit out, this is the best avenue instead guessing and replacing parts what does not need replacing, can get very expensive. this way it will help narrow down the problems. oil gauge is low, making sure you have proper amount of oil in the car with recommended weight, next, go ahead replace oil pressure switch, can be faulty/ fairly cheap to replace. if the switch is good you may have problems with the oil pump, worn-ed pump which not pumping enough pressure, this can lead to engine catastrophe; pump will need replacing.