Do you mean the light within the circle under the rev counter needle? If so, turn off the engine as soon as it is safe to do so. The oil pressure or the coolant temperature is in the danger range. Check the number of bars in the temperature gauge or an oil can symbol to the right of the light to see if oil pressure or overheating is indicated. Running the engine with low oil pressure will ruin it in short order. Oil level is not enough. The oil pump must be working properly. If you are lucky, a loose wire or bad sensor may be the problem. If the oil pump is the culprit though, it can take less than a minute for cams running dry to ruin the heads. Overheating will take longer to ruin the engine, but it isn't safe to continue running for long.