Mysterious Injury

I've been away for college for a while now, only getting to come home every once in a while for a weekend. I left my snakes in the care of my father and trusted them to be well cared for. I was able to deep clean their tanks today and I discovered what appeared to be an impacted snake.
Upon further investigation, this is below his vent and appears to be some sort of scab or something. It doesn't look good. It appears to be a thick, black scab, about the size of a dime. I'm afraid it may be infected because there is a greenish tinge to it. I have no idea what happened, how long he's had it, or what to do about it. The website won't allow me to upload any photos.
We were soaking him, thinking it was an impaction. Now my dad is insisting we should continue soaking him to try to soak the scab off. Is this okay? Should we just wash him with betadine?
His bedding is aspen shavings and he's got a large fake rock he hides in. There's nothing sharp in the tank. He only eats frozen/thaw mice, so it's not a mouse bite. We don't have any exotic vets near us, so going to the vet is pretty much out of the question.
Please help! I have to go back to school tomorrow and would like to be able to leave knowing he's getting the care he needs.

I know it can be challenging keeping a snake at home while living at college. How old is the snake? What are temps in the enclosure? What is the feeding schedule? Is the wound only on the skin?

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You were much more pleasant than someone on another forum, and for that, I thank you! If I could have him with me and/or delay coming back to school, I would!
He's about 6, I believe - definitely full-grown. He's fed every two weeks, eats one to two mice. I've requested a temperature check from my dad - I'll let you know. It's kind of difficult to tell the depth of the wound. The skin is kind of puckered around it and it's a pretty thick scab. After soaking it, some of the edge bits came off with some gentle cleaning with a washcloth. It's a bit easier to see - I think it's started healing on its own, which is good.
We replaced his bedding with paper towels to make sure there's no way he can get bedding in it and we sprayed it with Betadine twice a day starting last night. There's already a scab though, so I'm uncertain how much good that's doing. And it's on the bottom of his tail, so it rubs off pretty quickly.
I know I'm rambling, I just want to try to give you all of the information I can so I can get the best advice I can.

Too bad you can't show us a pic of the wound. That would really help a lot.

Any idea why you couldn't upload pics?

This link to upload instructions is from one of my other sites, but the procedure is the same:

http://www.faunaclassifieds.com/forums/showthread.php?t=304671

Just be aware that the size of the image has to be less than the stated limits. Often pics taken with a smart phone are pretty large, and that just doesn't work well, so size limits had to be implemented.