It is just mechanical cervical strain ,consult orthopedic surgeon get evaluated by clinical examination and xray

Thanks for asking me to respond. Sleeping workout a pillow results in the neck not being supported. Using a thick pillow is equally bad. Use a small pillow so that your neck is not under strain for 6-8 hours in the night. If pain persists for more than three days you need to visit the nearest ortho surgeon who can perform an examination and order xrays of necessary. I cannot prescribe meds as Practo prohibits me from doing so. Once pain reduces got will need to exercises involving the neck and strap muscles. Strong muscles will help support the cervical spine (bones in the back of the neck) and prevent recurrence of pain in the future. Good luck!