You probably had your neck in an awkward position while you were sleeping.
i've had my neck pop before and it resulted in almost unbearable pain if i moved my head even slightly. lasted about half a week and now i get scared whenever i feel my neck pop.
It'll most likely be a pulled muscle. Swallow some painkillers or ibuprofen and you'll be good as new.
try to look down towards your feet and see how it feelsit could be pulled muscles in the chest, back or shoulders too
there's so much pain my whole body freezes from shock for a couple seconds.