Headaches often accompany stress. Releasing some tension from your body through some simple yoga poses may help relieve some of your pain. Here are some very simple, beginner friendly poses which you can try. Try them for just a couple of minutes at the end of your work day 3 times a week. They will help get you moving a little, make you focus on something that is good for your body, and help you to wind down.
Cat Pose
Begin simply with your hands and knees on the floor in a tabletop position. Exhale and round your spine up. Inhale and return to the neutral tabletop. Do this about 5 to 8 times using your breath to lead your movement. How is this helping you? This helps to elongate your spine and separate your disks which can get compressed when you sit for long periods of time. Compression can affect the nerves which may be giving you headaches.
Eagle arms

This is especially good for relieving tension headaches. You can do this either standing or sitting cross legged. This really releases shoulder tension. Hold the pose for 5 to 8 breaths with left arm under right and then switch to right arm under left.
Child’s Pose

This is the fundamental resting pose of yoga. As you drop your shoulders and release tension your breath is directed towards your back. This helps push oxygen up to your neck and shoulders.
Legs up the Wall Pose
So easy, yet so powerful. Lie down on the floor near a wall and rest your legs up the wall. This allows the pooled blood in your legs to circulate easily helping reduce fatigue and anxiety. Stay here for as long as you like breathing deeply and fully.
Corpse Pose
This is usually the final pose of yoga practice. This is the time to slow down your breathing, quiet your mind, and relax your whole body.

All these poses, as well as a few more, can be viewed in this article from The Huffington Post: 10 of the Best Yoga Poses for Headaches.
To your health