Blinking White Light During Calls on Galaxy S10
The blinking white pixel near the front camera when you make calls, is simply the proximity sensor that detects if you are holding a phone to your ear, so it can turn off the display to prevent accidental touches.
The S10's Infinity O display minimizes the bezel, so the proximity sensor is now located at the top of the display. Communication apps such as Hangouts and WhatsApp may also enable the proximity sensor, and cause the blinking light to appear.
So when you see a blinking white dot while making a phone call, don’t worry as it is completely intentional