This exercise will improve the flexibility of your sternocleidomastoid muscle.
Start by bringing your right hand behind your back and side bend your head to the left. Then, turn your chin and eyes to look up and hold for 5 deep breaths. If you start to feel pain in the neck, tuck your chin.
To stretch your left SCM muscle, place your right hand across your left chest on your left sternum/collarbone area and apply a gentle pressure downward. Side bend your head to the right only going as far as you can tolerate. Avoid pushing through pain. If you feel pain in the back of your neck, ease off and tilt your chin down slightly. Now, turn your chin and eyes towards the ceiling. Hold for 5 deep breaths. Repeat on the other side. Perform this stretch daily throughout the day.