Can a very small umbilical hernia cause digestive problems?

Very unlikely. If the hernia is small and reducible (you can push it back in) it is unlikely to cause problems. If the hernia ever causes you pain or you cannot push it back in, that needs to be evaluated by a physician right away.
Umbilical hernia. Hernias can cause pain and more commonly when things are intermittently stuck or incarcerated in the defect. This is a sign that you should have this issue evaluated by a medical professional and consider treatment if it is frequent or changes your ability to do normal daily activities.