How is the sternum protruding?

There is a roughly rectangular bone in the chest, which is what you call "all the ribs", called the sternum. Anatomically speaking, the sternum is divided into three parts from top to bottom: the sternum handle and the sternum body, and there is a thin protrusion called xiphoid process below. Although it is also a part of the sternum, its shape and size vary from person to person and will change with age. What you said is normal, don't worry. Of course, no treatment is needed.