Skin Graft On Heel 5 Days Ago Very Strong Odor

Skin graft on heel 5 days ago very strong odor exists and graft is blackish to dark brown no sign of infection I did get blood work performed I had surgery 9 weeks ago and heel portion of surgery failed to close which brought on this graft I am diabetic a1c is 8 one is 3.4 and have a mechanical aortic heart valve. Question is should I be worried this wound has a very strong odor and surgeon could not answer why the bad smell. Along with dark color to graft? Almost scab like? Thank You !!!