What does it mean when the "change oil" light comes on and I've changed the oil 2 weeks earlier?

it means that the oil indicator needs to be reset. after changing the oil, pump the gas pedal three times with the key in the run position (position just before the motor starts up). three times to the bottom in three seconds. if the oil indicator light does not turn off, try again.

When you change the oil next time, reset the oil life monitor. It doesn't know the condition of your oil. It uses the number of engine starts and length of trips to determine when the oil needs changing. Resetting the monitor resets the cycle.

Yeah, the newer cars actually monitor the condition of the oil, but the older ones are just a counter...