Get a screen protector for your iPhone 8.. Now!
By far not the most durable glass.. This is it after about a week of use. No drops. With a case.
Are you referring to that line I see from the earpiece? If so, make an appointment at the Genius Bar of the nearest Apple store. It is not unusual at times for the glass to crack in unusual places, and if there is no sign of abuse to the device, it can be considered a manufacturing defect. I had a 4s back when they were new, and a crack suddenly appeared on the back of the device, and it was determined to be a defect and was replaced for free. Only Apple can make that decision.