tough muscle or hard tissue under left shoulder blade

I’ve had this muscle, ligament or some tough tissue that spans from under my left shoulder blade, all the way to my neck.
It seems to be aggrivated whenever I over exert myself.
It’s allways a dull ache and really seems to get tight when I work hard.
Whenever I have had my back massaged the person touching it says it feels like a long ligament.
What could this be?
Should I be worried?