The button you have been pushing moves a wire through a tube that bends across behind the instrument cluster. On the back of the speedometer is a switch that the end of the wire is supposed to flip, resetting the light. I have just had the same thing happen. The button will no longer reset the light.

You should be able to reach the switch somehow, without taking the instruments out, but, while I was waiting for the correct astral alignment to try, the light went out by itself.