I did some reading and debated on whether I should let it ride, especially since it only happened on one of my wheels, or if I should fix it. The consensus was it wasn't going to make the cheese unsafe to eat, but the black mold can negatively impact the flavor of the cheese. So, I decided to fix it.
It's not so hard to fix. I threw my cheese wax in the double boiler to get it melting and then went to task on getting rid of the mold. I simply cut the mold out of the cheese right through the wax, making three small divots in the cheese. I think I caught it pretty early and the visible portion of the mold only penetrated about 2mm into the cheese. It was fairly easy to cut out.
I also decided that this would be a good point to sample the cheese. It had been aging for a month to the day. I was nervous, but after cutting off a chunk and smelling it I was quite optimistic. The sour smell was completely gone and replaced by a very mild cream smell. I took the wax off (throwing it into the double boiler to join the rest of the wax) and sampled.
It was amazing! Honestly, definitely not the best cheese I've ever had, but definitely good and made all the more special knowing that I had made it. It tasted very mild and somewhere between a cheddar and a provolone. It's harder than a normal cheddar, which I can only assume is due to the acidification that caused the sour smell, but not at all crumbly. It was also probably hard because the way I cut it I probably got mostly rind. I'm very happy with how it's turned out so far.
I then cleaned the cheese surfaces with some white vinegar and cheese salt and let it dry. Once the wax melted I re-sealed the holes, first by dripping melted wax off a toothpick to fill the holes, then dipping the entire face of the cheese back in the wax a few times. I'm pretty certain I got a good seal this time. Then I sealed the end I cut off by dipping it in the wax directly. To be prudent I used six coats.
Happy cheesing!