You must be having muscle strain or spasm. Apply hot water formentation on painful area 3-4 times a day. Avoid strenuous activities which aggravate the pain. Take adequate rest. Consult physiotherapist. Physiotherapy treatment with ultrasound therapy and myofascial release will relieve the pain.
Health Tips
Use a thin pillow or cervical pillow while sleeping. Do not sleep without a pillow. Until the pain subsides, avoid lifting heavy objects. Take frequently breaks in between work.