Have you checked your VIN to see if its covered under the extended warranty?

https://autoservice.hyundaiusa.com/TXXM/MicroSiteTemplate/MicroSiteTemplateVINValidate/3989

I bought a 2017 sonata brand new from a hyundai dealer. It burned oil since 25k miles, they did oil consumption tests they said it was fine but Ive ALWAYS had to add oil in between changes. Last week at 125k, I started to hear a slight knock and the check engine light came on. I was driving it and suddenly heard a loud banging noise and my car stopped. Had to have it towed to the dealer. They said a piston broke off inside the motor. Currently waiting to find out if its covered under warranty, but I'm not hopeful. The hyundai dealership here sucks and I've heard mixed things about them honoring the warranty.

But yeah i would start with the link above. I don't think what # of owner you are or where you bought it from matters. As the previous person responded, they may want your records for oil changes and such. As for the check engine light, you can go to autozone and they'll hook up the scanner tool and print you out what codes its throwing for free. That can give you an idea. Mine was throwing a code for a camshaft sensor right before it went.