Hi ! Possibly during the time of your original head injury
, there was some effect on the cervical spine
as well and the effect is seen now as neck pain
due to cervical spondilytis. This cervical spondilytis could also be an independent entity not related to the original head injury. In both the cases the treatment remains the same like anti inflammatory drugs, and physiotherapy
to strengthen the neck muscles. However, if the symptoms prolong or increase, then I would suggest you to show yourself to a orthopaedician for a review and needful.
Wishing you an early recovery. Thanks.