When a vehicle goes into reduced engine power mode you should certainly be worried and have the vehicle checked out as soon as possible
The engine goes into reduced engine power mode to protect the engine and other parts of the vehicle.
Low oil level could be a cause of reduced engine power but your oil light should also come on as well indicating you have a low oil level.
Other causes of reduced engine power are bad spark plugs, bad spark plug wires, bad ignition coils, dirty or faulty throttle body, Vacuum leaks etc.
You really should drive the car or vehicle to a mechanic to have them check it out before the engine ends up worse off.
The engine reducing in power is done to keep from damaging your engine.