Long term hard mound on base of back the neck where it just meets spine gets sore and stiff what is?

The long-term hard mound on the base of the back of the neck where it meets the spine that gets sore and stiff is likely a lipoma. A lipoma is a slow-growing, benign tumor made of fat cells. Lipomas are usually soft, movable, and painless. However, they can sometimes become large and cause pain or discomfort. Lipomas are most common in adults between the ages of 40 and 60. They can occur anywhere in the body, but they are most often found on the back, neck, shoulders, and arms.

Treatment for lipomas is usually not necessary. However, if a lipoma is causing pain or discomfort, it can be removed surgically.