
I've had this so many times, not only is it painful but you use your neck for every movement you make so there is no relief. The only thing that works for me is to stand in a shower as hot as I can stand with the water directly on the spot. Doesn't cure it but improves the pain and increases range of movement.
Last month I had to rush my Doberman to the vet as she was clearly dying, fur dandruffy and motheaten overnight, hardly able to walk, trembling, roached back, abject misery, etc., etc. Just a 'cricked neck'. She had surgery for bloat at Christmas and made less fuss, so yes, it is very painful and takes at least a week to heal properly.