The bump you’re referring to, located just behind the ear, is most likely the mastoid process. This structure is part of the temporal bone of the skull and can be easily felt as a prominent knob or bump.
The mastoid process serves several important functions. It is an attachment point for muscles and ligaments, particularly those that aid in neck movement. Additionally, it plays a role in the anatomy of the ear, as it is situated near the middle and inner ear structures.
In some cases, any noticeable changes or swelling in this area could be related to infections, such as mastoiditis, or other medical conditions that may require attention. However, in healthy individuals, the mastoid process is a normal anatomical feature and varies in prominence from person to person.