The causes of a hard lump behind the ear that looks like a bone include the following: a. Consider that it is caused by swollen lymph nodes behind the ear. Lymph nodes belong to the body’s immune organs, and when local long-term inflammatory stimulation will cause lymph node enlargement. The swollen lymph nodes behind the ear are mostly caused by inflammation of the head and neck, including oral cavity and chronic otitis media, which cause the lymph nodes to swell and become hard, and then turn into hard bumps. Second, it is considered to be caused by sebaceous cysts behind the ear or other soft tissue inflammation caused by repeated stimulation. Hard bumps caused by sebaceous cysts can usually be characterized by local swelling, with flocculent objects resembling powder-like material spilling out when pressed, and painful symptoms during inflammatory episodes. If the bumps continue to increase in size and pain, you need to go to a hospital for an ultrasound examination to clarify. Pay attention to a light diet and eat less spicy and stimulating food.