Suggest Treatment For Painful Intermittent Muscle Knot In Left Shoulder

i have a block (tangle of muscles ) not able to get the exact description ...on the rear left shoulder ...like 10 cm apart from my spinal cord ...from the left...its like ...sometimes its there...sometimes its not...this is been happening for around 3 yrs...i am unable to bear it now...i just dont know what to do ....