Will the "Check Emissions" light turn it self off or do i need a OBD 2 reader?

Alright guys, today the "Check Emissions" light came on along with the spanner icon and the engine management light, does anybody have any idea what this could be? there is a strong smell of petrol, but maybe its always been like that and im imagining it.

if this sorts it self out somehow, will the light stay on or will it turn it self off? cheers lads.