It's not likely to be too much to worry about but instead muscular in nature.
The muscles in the upper back can become weakened in many people as a result of bowing the head to read or work and in turn the muscles in the neck become strained, pulling on the base of the skull to form "neck headaches".
Here are some exercises to try if you feel able, followed by some recommendations. Please be aware that if you take a lot of tea, coffee or salt the symptoms are likely to the worse:
- Standing, drop your head to one side while continuing to look ahead. Hold for 10 seconds and swap sides. Repeat twice more each side. To increase the stretch, drop the opposite shoulder.
- Standing again, lower your chin to your chest, hold for 10 and then look up to the ceiling and hold for 10. Repeat twice more. A more advanced version of this would be to lie on your front on the end of the bed with just your head over the end. Slowly nod it up and down to strengthen those same mack muscles further.
- Next, standing straight again, look over your right shoulder and hold firm for 10 seconds, then your left shoulder for 10. Repeat this 3 times. You'll notice more of a pulling or pinching sensation on one side more than the other, which shows you've targeted the muscle knot responsible.
- Finally, while sitting straight, jut your head forward and hold for 10, then all the way back and hold for 10. Repeat another 5 times and that's your 5 minutes done.
Those exercises stretch and strengthen the various neck muscles over 2-4 weeks when performed every other day. If you need extra help, try 200mg magnesium twice a day with food and apply some Atrogel (Arnica) before bed and upon rising.
Don't perform any of these if they cause you pain but by all means hold any position where you can feel a muscle being stretched gently. From my personal experience, these exercises can and should be done without aggressive or vigorous movements, they have rid me of 90% of my neck pain performed fairly gently.