Applecare+ on scratches.

Contact Apple directly and ask. If it’s just a cosmetic issue (doesn’t actually affect the ability to use you screen versus an actual crack) they may not cover it and you would have to pay the full amount for a replacement.

AppleCare does not cover cosmetic issues. And it would truly not be worth paying the full price to replace the screen on your iPhone. Especially if you don't use a screen protector, meaning a new screen will likely scratch again.

The simplest and least expensive thing you can do is to put a good quality screen protector on your phone, which will likely hide the scratch you've gotten and prevent any future scratches.