I found a painful little lump under my left rib cage and now its creating pain throughout my entire left side and now it hurts when I take deep breath?

Muscle spasm? Sounds like a spasm of one of the chest wall muscles. Try rubbing it, or applying a heating pad. Can also try topical agent such as Myoflex cream or aspercreme. Does not sound like a hernia due to location. If severe and unrelenting, may need to go to the ER for a more complete evaluation.