Here's a close-up of the blemish, which is positioned a few inches up on the cactus' back side.
Of course, I think it's really a bud for a side growth. So, my special cactus may have a new "arm" very soon.
This is especially exciting because this is probably my fanciest and most treasured cactus. I can't remember what it's called, but this cactus is originally from Mexico and is now sadly extinct in the wild. It grows in a pillar and has this very cool, wavy-looking exterior--almost as if it's melting in the heat. My parents bought it for me a California Cactus Center many years ago to celebrate a promotion at work. It now sits in a place of honor in one of the cactus planters Dakota built into our patio.
I am delighted that my "Celebration Cactus" is doing well enough to grow another limb. Perhaps, if it gets big enough, I can take a cutting and grow a new fancy melting cactus to keep this one company. Or, even better, I can grow another one to give as a gift.
For now, I will have to be patient. The pimple is quite small, and I don't want to make the cactus too self-conscious.