It means it was too much fatigue during the stretching of your neck. It would be better if you do some stretching that would not force your neck.

 Neck pain can be lots of things. Poor posture (my problem), sinuses, pulled muscle, tension and stress. If it's not sinuses and allergies you may wanna have a mri or a chiropractor look at. Always talk to your regular doc first tho. They know you the best. My chiropractor had me doing these exercises that helped me, I have a slipped disk in my c4 (bottom of my neck). Ytake your two fingers and put them all your forehead and push your head forward against it and hold to count of 5. Then do that with all sides your head once a day. It strengthens your neck muscles. Hope it helps!♥