A tight neck and possible trigger points in the muscles can cause referred pain and symptoms like headaches.
Here is one info site
The Trigger Point & Referred Pain Guide

Search our site or Internet for trigger point information and see if it fits. Some TRPs are self treatable. Some are harder to reach yourself lor near side of the neck where artery and nerves are.
Quality PT is a good starting base treatment if you find trigger points or for a chronic sore neck.