Something in my neck popped and now I can't move my head or my arm!

Lily-Anne
Yesterday after brushing my hair I shook my head slightly and something in my neck just gave way. It made a popping sound and was incredibly painful. I now cannot move my head or my left arm, it hurts to the point I am sitting here crying. 
I have barely gotten any sleep because of it, even walking to the bathroom this morning was agonising! 
What can I do? 
I urgently need advice!