turn you cap at least two to three full turns. The light should go out
within a week. Don't unscrew it and tighten it, won't work.
If it doesn't go out you can buy a new HYNDAI GAS CAP from your
dealer...NOT A STORE BOUGHT ONE.
As long as teh car isn't idleling rough or stalling, That would be a sign
of a bad oxygen sensor........... then it should be fine.
Nothing else should be wrong with your car other than teh gas cap.