DIAGNOSIS A stuck or dead sub-pixel on the VA panel. A black dot is usually dead. A colored dot is often stuck.
FIX For a stuck pixel, try a pixel-unsticking video on YouTube. Run it full-screen at the monitor's native resolution for several hours. This can sometimes revive stuck pixels. For a dead pixel, there is no software fix.
IF THAT DIDN'T WORK Check Samsung's warranty policy for pixel defects. Their policy often requires multiple dead pixels in a specific zone for a warranty replacement. One central pixel may not qualify. Contact Samsung support with your serial number to check.
HEADS UP Do not press or massage the screen. The curve makes the panel fragile. Excessive pressure can create more dead pixels or cracks. This voids the warranty.