engine management light 94 f astra

Hi im a newby on here and was wondering if anyone can tell me what the light
on my dashboard means.

I think its the engine management light but am unsure, it looks like an
engine with a lightning bolt thru it!!!

WTF can I do to get rid of it coz it s sooooooo annoying.

The car itself has done 116K!!! runs like a dream and stops and keeps
passing MOTs with little or no work to do, has BIG BORE exhaust and
induction kit advanced timing and runs on super-unleaded.

Car itself as I say runs fine is OK on accel and ticks over without a
problem.

I will point out I lowered the suspension 40mm a couple of week ago and a
little bit of oil dripped from the diff casing when I pulled the driveshaft
out and havent replaced the oil just yet(bad weather)

Can anyone please help coz its driving me nutz.

Regards