Thanks for the additional information. I really appreciate it.
So, from your description, it definitely doesn't sound like anything you really need to be too worried about.
Since you were gone for a week, and since I suspect he's not going to tell us how he hurt himself, we're just guessing at what caused that scab, but there are lots of things that could have caused it...bug bites, injury by something in the environment (like running into a branch or part of a tree) or even playing rough with other dogs.
The good news though is that it sounds like it's already well on it's way to being healed. That pink skin you described under the scab sounds like granulation tissue...that's completely normal and healthy to have under a wound like this. I'd only be worried if you notice swelling, heat to the area, discharge, or if he stops eating/drinking/behaving otherwise normally, as they can be signs of infection. It doesn't sound like that's an issue here.
I'd just give it another week or so and the scab will likely heal on it's own and fall off with no ill effects to your pup.
I hope this helps.