The sternoclavicular joint itself is more prominent, and the thin man is more prominent. Leave it alone if it doesn't hurt or itch. Totally normal.

The clavicle is S-shaped, not a straight stick. Don't worry.

There should be a dent in the upper sternum. Since you have a protrusion, it may be deformed, but there are no important nerves and blood vessels passing through the notch on the sternum, so I think you are more likely to have no symptoms. If you don't feel sick, don't worry. It's not too late to correct the symptoms. Good luck!