Hey I Have A Open Womb On The Lower Part

Hey I have a open womb on the lower part of my stomach where I had a midline ob surgrey and after four weeks I got infection and have been packing it twice a day now for the last 4 weeks or so and today my husband was changing my packing and notice a black round spot that is a little smaller than a dime...he tried to wipe it off when he cleaned my womb..but it would not wipe off..its got me really worried..cause I have been through a lot the last year with trying to get well....do you know what it might be and how it is caused...because it piped up over night