I've had the phone for a few months, and I've always had dark colour scheme on, so I'm not sure when this occurred. Could this be dirt under my screen protector, wouldn't that definitely show a bubble?
I enlarged the picture to the maximum and at maximum magnification you can see that it is not a dead pixel but some irregular dirt, even if under the glass cover of the display, but it is dirt. Dirt had to get there as soon as the phone was assembled in the factory.
