I definitely don’t think it’s dirt. The wounds appear concave and various degrees of colour which would suggest it’s an injury of some sort. Not sure if it’s rot, or if it was from a cut, or even burn, but I’d definitely take your snake to a vet and get it checked out.
I’m sorry to hear about that, that really sucks. If you can contact the breeder ASAP that would be best. It’s harder to get blamed for something when it’s only been a week.
Until you can get your snake checked out, just look for further signs of rot and RI, and any abnormalities in feces. Take note of everything and inform your vet.
I hope all goes well for you.