Welcome to Healthcaremagic.
I have gone through your query and understand your concern.
I Suspect you may have Muscle strain
My advise is to take bed rest
for 3 days. Please lay flat without using bed or pillow.
In addition, take some pain killers like aspirin or diclofenac
If the pain persists, then consult an orthopedician with x ray neck.
If he advise please take CT or MRI scan neck for further management.
Hope this helps.
Please reply for further queries.
Wishing you good health.