4 yr old fell hard on stomach before putting hands down (pretending to be penguin, 2 legs in 1pyjama leg). said stomach hurt. risk of internal prob?

Very, very small.: Thankfully 4-yr. Olds are resilient. They are not very tall; therefore, the velocity generated by a fall, if standing on their own feet, is almost impossible to cause internal injury. Nonetheless, there are oddities such as a swollen spleen or kidney that might be of concern. Children jumping off tabletops or trampolines are much more worrisome because the added height increases the impact force.