Hi. It seems like you're suffering from trapezitis. This basically means that the muscle that supports your neck and shoulders is sore. It could be because of prolonged bad posture (keeping your neck bent for long hours) and this might even be associated with cervical spine mis-alignment. It is frequently caused in people who have an occupation which involves long hours of using a laptop, or people who have greater phone usage.
Next Steps
Kindly get evaluated by an orthopedic doctor or a physiotherapist.
Health Tips
Active movements of your neck for warm-up in the morning, looking to left and right, tilting your head by touching your ears to shoulders, and nodding movement, 10 times each would help for starters. You could also benefit from a hot-pack for 15 mins, morning and evening.