I have discovered what appears to be a lump under my rib cage, though it could quite easily be my actual rib which is lumpy. I used to smoke, although quit about five. Pain under the left side of the rib cage is experienced by many people around the world, even by those in sound health otherwise. The reason for such pain can be. Home > General Health > What to Know about Pain under the Left Rib Cage. What to Know about Pain under the Left Rib Cage Discomfort on left side of stomach below rib cage, mostly when i m sitting i feel as if something is bulging out. but nothing is. I m not constipated. Bowel. Right Rib Cage Organs. The rib cage is the part of the axial skeleton that protects the vital organs within the thoracic (chest) cavity and the upper part of the. I have a large lump under my rib cage on my left side of my back. I just noticed it recently. What could it be? Rib Cage Pain on Left Side. Although costochondritis, intercostal muscle strain, or rib fractures could be the common contributing factors for pain on the left side. Ive recently noticed that the left side of my rib cage sticks out a lot more than my right side. When i stand up straight/leaning back slightly and look down at my. I have noticed a lump on the lower right side of my rib. Just below the rib cage. It can be painful when pressed and is sometimes (not always) accompanied. Are you experiencing pain under your left rib cage? This is a common problem faced by many people across the world, even those who are in good health otherwise.