It could be were sweat has collected in the naval and has started to smell. Each night after you take a bath or shower just clean it out with a swab and it should start smelling better. If it still has an odor after a week or becomes red and sore then see your physician because that may be a sign of an infection.
There Is A Strong Odor Coming From My Navel. Is It An Infection And What Are The Treatmnts Needed For This Condition?
Before you think it's an infection it might just need a good cleaning. Take a cotton swab and some rubbing alcohol and clean really good at least twice a day for about a week and it still has an oder see your physician.