Why I have thick vertical bar suddenly appear on my display?

Try disconnecting the display cable, inspecting the pins both on the cable side and the port side for damage, dusting them with compressed air, then carefully reseat the cable. If that doesn’t help, you can try replacing the cable itself (cheaper than replacing the display). In my experience though, this specific visual glitch is normally due to damage to the display assembly itself and not an issue with the display cable. It may also be worth checking with an external monitor to verify the issue is not with the graphics, but rather the hardware of the display. My best guess is that the display assembly itself is damaged and would need to be replaced.