My dog has a laceration and it is starting to stink.?

It was done while we were gone the other day and when we got home too much time elapsed in order for him to get it stitched. He has been on cephaxalin for two days. Tonight when I took off his bandage to change it I freaked. It stunk and was getting black in some places. I tried to call an emergency vet and the only one we had around us has closed down. I cleaned it really well with saline solution and put anibacterial dressing on it. Will he be ok until tomorrow. Does anyone know if this is normal for a deep laceration? I didn't know if it might be part of the healing process. I really don't think it is if it smells and looks the way it does....please help