I have a new Lenovo laptop, I accidently clicked a key but I don't know which one it was, my sound has completely stopped, any suggestions?

Restart the computer to bring back original settings. If that does not work, run a RESTORE to any date before you accidentally hit wrong key.

Yes you hit the volume mute button look close it's a little speaker with a slash mark through it there's a Volume Plus and there's a volume minus if you push the Volume Plus button it should make your volume come back even if you can't find the mute button