White screen on the left side of my macbook air

Try and see if you need to install any software updates

If not, boot the Mac in the safe mode to see if the Issue persists. If the issue does not persist in safe mode it might be caused by an external piece of software. You want to review the external software you've installed to your Mac if this is the case

The steps of booting in safe mode differ whether you using an intel mac or a Mac with apple silicon

Start up your Mac with Apple silicon in safe mode

1. On your Mac, choose Apple menu  > Shut Down.
2. Wait for your Mac to shut down completely. A Mac is completely shut down when the screen is black and any lights (including in the Touch Bar) are off.
3. Press and hold the power button on your Mac until “Loading startup options” appears.
4. Select a volume.
5. Press and hold the Shift key, then click Continue in Safe Mode.
6. The computer restarts automatically. When the login window appears, you should see “Safe Boot” in the menu bar.

Start up your Intel-based Mac in safe mode

1. Turn on or restart your Mac, then immediately press and hold the Shift key until you see the login window.
2. Log in to your Mac.
3. You might be asked to log in again.
4. On either the first or second login window, you should see “Safe Boot” in the menu bar.