Smell from donor site of gum graft?

I had a gum graft 3 days ago. Doctor put a piece of collagen on the donor site on my palate, and I have been wearing a plastic retainer, made by the doctor's office, to protect it. The site appears to be healing well and pain is minimal- but it smells horrible, kind of a rotten meat odor, and has a foul taste. Is this normal?