I have a very small bump (smaller than a pea) behind my belly button. If I put my finger inside and search around I can feel it. It caused me some discomfort, but no real pain, and it is not getting worse. It may have shrunk a little bit. If I press it, it s tender, but again no real pain. I am not sure if this could be the beginning of an umbilical hernia . It doesn t seem to reduce when I press on it, but then again, I m not a doctor. Could this be a cyst of some sort?