Try these steps to reset your user account password:
Shut down your MacBook Air .
Press and hold the power button (Touch ID) until the screen says "Loading startup options".
Choose Options, then click Continue.
If you're prompted for an admin password, choose "Forgot all passwords?". If you're prompted to authenticate with your Apple ID, do so to continue.
You should now see a window with four options: Restore from Time Machine, Install macOS, Safari, Disk Utility. Don't choose any of these; instead, go to the menu bar at the top of the screen and click on Utilities. Then, choose Terminal.
Type "resetpassword" without the quotes and hit Enter (Return).
If FileVault is disabled, you should be able to reset your password without issue.