the line in question looks something like this:
Code:
linux /boot/vmlinuz-linux root=UUID=xxxxxxxxx-xxxxxxxx-xxxxxxxxx <possibly_more_options>
and you have to edit it to look like this:
Code:
linux /boot/vmlinuz-linux root=UUID=xxxxxxxxx-xxxxxxxx-xxxxxxxxx <possibly_more_options> nomodeset
be aware that you don't accidenatlly put the nomodeset on the beginning of the next line, instead of at the end of that line.
in any case, once you started X with sudo, it might have done more harm than good.
it is possible that some files in your user's $HOME are now owned by root and X can't start anymore.