Dead pixel(s) covered by AppleCare+?

Since a few days I have a dead pixel at the bottom of the screen near the dock in macOS that is completely black.

To get a good look at this spot on my screen, I used a flashlight, but I didn't see any foreign material on my screen. There is also no impact to be found in that spot. I've tried to polish that spot three times with Apple's Polishing Cloth, but there's nothing there on the screen.

In which case can this be repaired?