I Am Experiencing Constant Tension In The Left Side Of

I am experiencing constant tension in the left side of my posterior neck. Pain seems to increase whenever I extend my neck and rotate my head to the right or simply tilt my head to the left. I also noticed that there is a hard lump located on my left occipitalis muscle. This discomfort seemed to arise when I started working out about 6 weeks ago and has not subsided. When I attempt to lift waits I get the worst headaches I've ever felt as a result and it seems that my entire head is being squeezed.