Suggest Remedy For Pain In Neck,upper Shoulder And Lower Arm

I have a muscle-sprain-in-neck since 1 month, the pain is getting unbearable when in laying position(sleeping). The pain is sometimes in left side of the neck, left shoulder, in left biceps(upper arm) and sometimes in lower arm. The pain is not constant at one location but keeps changing around the left side of the neck, shoulder upper and lower arm. I fell down from the bed a couple of months ago. Laying down and sleeping is becoming very difficult. Please suggest some treatment.