Can't boot my android after changing permissions

I recently rooted my android (Nexus 4). I wanted to make /system folder permissions 777, I needed that for another application. I got Root Explorer application, and changed permissions to 777. Then root folder disappeared and hanged up. I tried to restart my phone, but now it doesn't even boot up. What should I do? ... Please, don't tell me I bricked my phone.. It was just permissions, nothing more... I have no idea how to recover now.

When I do adb shell, I also get mesaage:

/system/bin/sh: /system/etc/mkshrc[9]: getprop: can't execute: Permission denied

Also I can't go to root mode (adb root) in console, from $ to #.. so it means.. I even can't change permissions anymore?