Put the car on jackstands and drain what's in there and refill it. I'd replace the oil filter even if it's not due as the o-ring/gasket might have failed and letting oil leak. You can try to refill it slowly but your better off going with a fresh oil change as you might overfill. I would think if the sensor was failing, it would be on constantly or come on randomly. It's possible if your oil level is low enough that the pickup simply goes dry under the right circumstances (like left turns) and that's why your getting the light. Throw a a sheet of cardboard under your engine when you park it tonight and see if your leaking from anywhere.