This is called the inion, the bump on the back of the skull that is common to most of us. If this bump feels “mobile” (you can move this bump under the skin with your fingers), this could be a lymph node.
If this is the suboccipital ridge of bone or the inion, you don’t need surgery as this is normal. If it is a set of swollen lymph nodes, you will need to see your primary care doctor.
