I have a small lump two inches below belly button that feels bruised when I touch it.  Also lower abdomen and lower back have dull ache.  Also nausea?

?hernia. This could be an umbilical hernia and if it's not fully reduced it may produce those symptoms. I recommend that you consult an abdominal SURGEON for evaluation as soon as possible in view of your current symptoms as an incarcerated hernia should be treated as soon as possible to avoid more serious complications like strangulation of a piece of intestine.