You may indeed have mold, but before you cut please answer a question. Did you happen to repot this plant without removing all of the old soil? I wonder if this was present before you repotted, hidden by soil, and is not actually mold.

Many growers use peat pots, like Jiffy pellets, that expand when water is added. They look like this -

That netting is supposed to hold the substrate and they say you don't need to remove it and roots will grow through it. Well, it does not biodegrade. I have found it in my flower beds years later. And, of course, peat is not good for succulents. Not removing it means that the plant is still growing in peat, no matter what else you fill the pot with.

See if this 'mold' feels a little like fabric or netting. If so, remove it and let the plant rest a day for roots to heal a little. Then repot. If it is not netting, you may want to follow nik's advice.

BTW - it looks like you have used commercial cactus soil in your pot. You need to add at least 50% perlite or grit to this mix (no matter what the bag says). And we have had some members find that there is mold in this soil, too.

Good luck! Let us know what you find.