What are some reasons for pain in rib cage area? its just on on side and feels like a bruise.

Costochondritis mayb: Trauma or injury obviously, but you would have reported that! sometimes even "minor" truma or even exercise or activity can cause an irritation of the ribs or the cartilage, called costochondritis. This can feel like a bruise. If associated with a deep breath, it can be another kind of inflammation called pleurisy, which is more serious. The location of the pain also suggests other causes.