I just noticed there were two threads about this. I posted a message on the other thread, but that one didn't have photos. I've only seen crop burn in books/, but that sure looks like crop burn to me. However, as others have said, if your baby is already weaned and is eating well, the worst might be past. Not all cases require surgery -- many only require supportive care while the scab heals. I hope you can see the vet tomorrow and get good news.