Stiff neck. There is some other reason.

My daughter had fever (100-101 degrees) , runny nose and cough 7 days ago. She was on medication. After fever,  she started complaining of headache. She was prescribed hatric 3 medicine. After which she used to feel comfortable. But after 5-6 hours she again used to complain about headache in forehead. She used to wake up at midnight because of the pain. Now her headache is better but since yesterday night she is  complaining of stiffness in her neck. After giving her calpol ,she feels better and completely normal. But after 5-6 hours she again complains of pain in neck. She does not have fever from last four days and her cold is also better. Is the stiffness because of some sprain or else there is some other reason.