What Causes Protrusion Of Chest Bone Along With Pain In A Child?

My son is 11 yrs old and he occasionally complains of chest pain. I've already had him checked out twice and I was told that he has a heart murmur but nothing to be worried about. I was told that it would go away as he got older. But he was just complaining about pain again and his chest bone looks significantly raised on the side where his heart is. Why? I'm extremely worried!! Please I need advice, I don't want to scare him by taking him again.