1994 Astra, High revs at startup particularly when cold?

The engine revs high when cold but sometimes when it has been runing for about 30 minutes it revs normaly. This problem only hapned rarely but quickly went away each time but now it is all the time. Also there is an orange light comes on in the dashboard bscide the spedo. The light has an engine symbol with a lightning strike through it. The car is 1400cc single point fuel injection 1994. Please have you any ideas.