As @mikeselectricstuff says, I think sunlight reflection seems a possibility, hard to see what else would concentrate so much heat in one spot, especially as it looks to be offset from the headlight beam.
I remember having a whole load of cassette tapes (remember those?) melt after I left them on the dashboard of a car years ago, the sun had somehow been focussed on that area and they got hot enough to melt so all the cases were distorted and stuck together. IIRC, cassette cases were made from polystyrene, that has a transition temperature of around 110°C, so exceeding that on a dashboard is possible. The glass transition temperature of the polycarbonate that the lens is made from is a fair bit higher, around 150°C, but it seems possible that the sun might be able to produce that sort of temperature inside the light unit.
Hi Jeremy, thank you for your opinion I have been living in North queensland Australia but my car always keeps in the shade.I have some time go out and about to town but never leave parking in the open all day and night time parking in my garage since Aug 2019. I am very pleased to hear your comments. Thanks.
Hi Donald, it's not affect the beam so far.
Today I picked up the car he said he going to make claim to replace the headlight but he would not sure what exactly caused and depending on Hyundai Australia. I will keep posting, thanks for your comment.
However Hyundai will not be able to assist with this repair as it is considered damage due to external/environmental influence.
Customer Care Officer Hyundai Motor Company Australia http://customercare.hyundai.com.au
Phone: 1800 186 306
I think they might be correct in regards 'outside influence', it may be that a random solar reflection has focussed itself off the back reflector. Part of the issue with 'crystal', rather than diffusing, headlight lenses.
You have some super-hot Sun down there, I spent a year in SA and was surprised at how much hotter the Sun felt there than anywhere else I'd experienced (which was probably South California, not exactly known for insufficient sunlight).