So after banging my head for 2hrs and 100 different articles, I managed to brute my way to success.
- Use finder to change permissions of sudoers file. Right click>Get info>Sharing and Permissions.Change it for all parties including 'everyone' to read & write. Not sure if this step is necessary though.
- Delete sudoers file from /etc/ using finder after making a copy of it.
- Shift new sudoers file back to /etc/
- Use this command to restore your sudoers file https://apple.stackexchange.com/a/394943