Unable to change key binds

While editing my keybinds, I clicked on toggle full screen planning on changing it to something else. But when I clicked on it, it didn't allow me to change the key bind. The main part that I'm complaining about is that it got stuck on left click, so now left click can't do anything but toggle full screen. And thanks to that, I am unable to click or change anything, it just toggles full screen.