My daughter has a knot in her stomach what could it be?

Along midline?: If you can feel small knot under skin along midline of abdomen between belly button and chest, consider ventral midline hernia. Usually painless, no external skin changes, may stick-out more with crying or straining. Definitive tx is surgical repair but many smaller hernias may never enlarge or require repair. To dr asap if skin changes, painful or increasing in size.