Civic EG

So my B16a head gasket was leaking and had to be replaced, so i replaced it also the head got warp a little so the head had to be shaved alittle,
So all thats done and the engine work fine now but as soon as the engine heats up the CHECK ENGINE light comes on and doesn't come off until car is switched off.the car is not overheating or anything works normal.
Whats that about? why is it doing dis?

have you checked to see what CEL code its throwing??

whats dat? the led in the ECU?