When the baby is developing in the mothers womb, the pinna / outer ear is formed through a series of complex steps where different areas of skin and cartilage join together. Here is a video that shows how the development takes place. If the structures don't form properly, the baby may have a small malformed ear (microtia), or a pit could be left between parts that should have fused together (pre-auricular sinus).
A pre-auricular sinus is seen as a pit opening just at the front of the ear, near the ear canal. Many people have one, and if it doesn't cause problems then no treatment is needed. However, if it becomes infected, the pre-auricular sinus will need to be excised.
Pre-auricular sinus surgery
Surgery is quite complex. The pit opening that is visible is just the tip of the iceberg, usually there is lots more infection hidden deeper and heading forwards onto the cheek. To reduce the possibility of recurrence, all the infected area needs to be excised. This means that scar used is often much larger than just the pit opening. Despite this, recurrence is still a possibility. Very rarely, surgery could result in an area of skin loss as well, which may require a covering dressing for a period of weeks whist we wait for the area to heal.
Once infection has happened, surgery is usually recommended. If you notice that the pre-auricular sinus is painful, swollen or discharging, make sure that you seek medical attention and involve ENT surgeons at an early stage.