Hi, If I were your treating Doctor for this case of severe pain under the left rib cage, I would come up with three possibilities, these include: The first possibility is of tongue or cheek bite during vomiting. Diagnosis can be confirmed by examination of mouth. To help control the vomiting, you should always keep head of child,give him water to rince outh. Also take some domperidone or ondansetron syrup ; if the symptoms are severe, then you may need drugs like proton pump inhibitors. The second possibility is of febrile seizures. In this case he should be observed by neurologist to rule out seizure cause. The last possibility is of erosive gastritis. For this purpose you need to get an occult blood stool test,stool culture for flora and sensitivity to antibiotics. Hope this answers your question. If you have additional questions or follow up questions then please do not hesitate in writing to us. I will be happy to answer your questions. Wishing your son good health.