Accidentally ran chmod -R 777 /?
I'd worry a lot – because what you did is equivalent to opening all doors and windows in your house wide, and then go sleep. The entire world (figuratively spoken) now has access to everything the chmod managed to touch. Not having run it as root might mean damage is not that extensive – but it could still be enough for the one or other mishap.

To fix up what might have been broken, unfortunately the only safe way is a factory-reset – as it's hard to say which files/directories have been changed and even harder what their previous "access levels" were.