How do i get check immisions light of my modus?

The RAC put a code reader on my modus because the check immisions light was on, the fault was with the EGR valve,i took it out and it was choked up solid,lumps as big as marbles, i sucked all the crap out of the housing with a modified tube on my garage vac,then i cleaned the valve in petrol till it was like new,i refitted it and the car sounds totally different now, i thought the lights on the dash would go out automatically now i`ve sorted the valve, but they haven`t,( how do i remove the check immisions light on the dash, Thanks in advance if you know how.