Moving torso/lifting objects/etc causes sting/stab/burn pain on left side sternum. breathing doesn't exacerbate. costochondritis or intercostal pull?

Costochondral Injury: Teenage male with left parasternal pain aroused by mechanical stress of this region might have injury to junction where cartilaginous extension of rib joins sternum. Localized pain elicited by palpation of this junction is expected and is diagnostic. Heat, rest, avoidence of strenuous lifting, pushing, ; pulling should be accompanied by resolution in 2-3 weeks. If symptoms not resolve see doctor.