Suggest Treatment For Lump Near The Shoulder Blade

I have a lump or knot right beside my right shoulder blade near spine. It hurts off and on and depending how I sit or lay down bothers it. I asked my husband to rub my back and he could feel something there but he said it didn t feel round like a knot and when he pressed on it I could feel a numb/tingling feeling on the spot. What could be the cause and how do I treat it?