Sound won't work on my MacBook air

Hi there,

My sound has suddenly stopped working on my MacBook air. It was working earlier today and then suddenly stopped when I went to watch a video. I thought it was strange so tried to play a song just incase and again there was nothing. I searched it to see if I could solve it and couldn't. I went to the sound section in system preferences and could not find the 'internal speaker' option for sound, only the headphone option, which of course happens to be useless for me as I have bluetooth headphones. Also before you ask, nothing was muted- I'm not that stupid.

I have restarted, updated and turned everything on and off again but still no applications will play sound. I would really love an at home solution as I do not live anywhere near an apple store and am a student so I am always busy!

Any help will be much appreciated.

Dara.