Welcome to HCM.
Most probably it is swelling in the subcutaneous fat. It is also known as hump. Sometimes it is painful. If possible upload a clinical picture of your neck and upper back. Usually local measures such as physiotherapy
may help to relieve the pain. We need to see your posture and if you have protruding neck with abnormal spine curves. Is it painful? is it just looking bad? whats your concern pain or cosmesis? Thanks.