Please tell me what is it mean when there's a sharp pain in left side of chest like right under left boob?

Costochondritis: In fortyish female chest pain aroused by direct palpation often reflectscostal chondrites & inflammation where rib joins cartilage; between rib and the sternum. Point palpation of this region often arouses exquisite pain. A cortisone injection can dramatically dissipate. Most generalist doctors can adequately discern, unless they refuse to touch you and just get an ekg, as some will do.