The Malfunction Indicator Lamp (MIL) generally comes on when there's a problem with any of your emissions related hardware(e.g. Catalytic Converter, Oxygen Sensor etc).
Unless it's a flashing MIL, which indicates Misfire, in general its OK to drive the vehicle.
However, you should have the fault codes checked with a Diagnostic Tool, which will exactly tell you what's wrong with the vehicle.