Pain in the tummy (abdomen) is a common problem in children. The right side of the lower part of the tummy (below the tummy button) is called the right lower quadrant of the abdomen. The main issue when pain is in this area is whether or not the diagnosis is acute appendicitis, but there are many other possible causes.
This is a companion discussion topic for the original article at https://patient.info/signs-symptoms/right-lower-quadrant-pain/causes-in-children