|...or get a magnifying glass :D lol|
are you sure you can't see enough to guess your way into changing in the same manner you changed it in the first place? right-click the desktop and choose the option furthest down in the bottom, then click on the last tab and adjust the slider to the left, then hit the button farthest to the right which is apply.
if you have a branded pc you might even have short commands for changing the resolution.
another way could be, if it's a laptop, to boot the pc up with an external tv/monitor, that'll most likely force down resolution.
a possible fourth way would be to change your monitor, i.e. borrow someone elses. I'm not really sure but I think the resolution would be lowered.
a way that will most definitely work though is boot into safe mode and uninstall the VGA driver (display driver). reboot in normal mode and download and install new drivers.