For some cars if it runs fine and you dont notice any missing/stalling/loss of performance,unplug your battery for 5-10 minutes,if the light goes off and never returns..problem solved..if it comes back,replace gas cap,(cheapest thing to do) Then depending on mileage,tune-up or else take it in if you are not mechanically inclined to do so..
My 2002 Dodge Ram 1500 4.7 L check engine light came on,it was the gas cap !! 285,000 original km,only non normal wear problem ever ...gas cap... now that is what I call reliable !! Gas cap,brake pads,tires,oil,gas..about 1,000 washes 200 polish jobs and 2000 litres of armor all...and it still looks/runs/drives like new !!