Maintenance light on, what is wrong?

So just today my Main Req'd light turned on and was flashing after I filled my car up with gas and went away. When I turn my car on again it flashes. It hasn't flashed before I filled my tank. I have a 2001 Honda Civic and never have had any problems with her. Every once in a while the left blinker blinks really fast, and I know that means one of my lights is about to go out. Other than that i don't know what it could be.

Is the gas cap loose? That will often turn on a check engine light.

It's your fetzer valve. Prepare that Fetzer valve with some 3-in-1 oil and some gauze pads, and I'm gonna need 'about ten quarts of anti-freeze, preferably Prestone. No, no make that Quaker State.

As ADB said check the petrol cap is on properly and tight