Hard lump in back of neck one inch from hairline in trapezius or between sternocleidomastoid. have had for a year and i tense my shoulders, what is it?

Many possibilities: How big? increasing in size? painful? history of infections? history of cancer? how deep? what does it feel like? swollen lymph nodes in the area? redness to the skin? does it move or is it fixed in position? drainage? fever? itching? fatigue? Large number of possibilities, benign cyst, fatty lump (lipoma), enlarged lymph node would be common, have a doctor check it. Most serious, but rare, cancer