That can be a wide range of issues. One of the most simplest is that the gas cap is not secured correctly. If retightening the gas cap does not help, take it to a dealer for service. That will be covered under warranty. However, I would recommend that you have some video or photo of the check engine light on, because the dealer may not do anything unless they can reproduce the problem, or at least have some proof that it actually happened (per instructions from Hyundai Motor America, who reimburses the dealer for warranty repairs).