A hard thing protruding from the bone behind the ear may be osteophytes, bone tumor, etc., or it may be a normal mastoid. 1. Osteomalacia: a hard thing protruding from the bone behind the ear may be the manifestation of osteophytes, the cause of osteophytes may be caused by local trauma and inflammation. 2. Bone tumors: long tumors in the affected area can lead to a hard thing protruding from the ear, which should be identified by imaging examination and pathology biopsy if necessary. 3. Normal tissue structure: there is a bone behind the ear called mastoid, bilateral symmetry, due to the good development of mastoid, mastoid bone is relatively hard protruding, there is no redness, swelling and pain, which belongs to normal tissue structure. Patients with a hard bump on the bone behind the ear should actively seek medical attention, do not judge on your own to avoid delaying the condition.