Sounds more like psoriasis, especially plaque psoriasis, than callouses. Google around for photos and descriptions of symptoms. Could also be "ringworm," a common skin fungus that goes after our sweaty bits.

I've had plaque psoriasis and psoriatic arthritis on and off for decades, due to an autoimmune disorder -- Hashimoto's, a thyroid disorder that's involved in a seemingly unrelated grab-bag of annoying symptoms. Right now I have an outbreak of plaque psoriasis because I've been taking a bunch of NSAIDs for two months, along with Prednisone, to battle a chronic upper respiratory inflammation. But if I take any over the counter NSAIDs for more than a few days per month I get plaque psoriasis, mostly in my scalp, behind the ears, back of the neck and, when it gets really bad, in the webs between my fingers. When those crack it's really painful.

Topical steroid creams help. I get the best results from Lidex cream. Pricey but lasts longer than OTC cortisone creams because it takes very little to be effective. My current tube of Lidex is going on 20 years old and still works.

But the most effective treatment is to identify the causes that provoke psoriasis or ringworm and treat that. Eliminate meds or foods that trigger the outbreaks. As soon as I quit taking aspirin or ibuprofen daily mine will clear up within a few days. Been there, done that, many times over the decades. I've mostly switched to CBD and occasionally kratom for chronic pain, but in the case of this upper respiratory inflammation, so far the only thing that helps is Predisone. And my docs don't like to prescribe it too often because of my thyroid disorder and early onset osteopenia. I also use a lot of inhalers for asthma and allergies, which may aggravate the condition: fluticasone, Asmanex, albuterol. That stuff is usually safe and doesn't cause problems in otherwise healthy folks, but for some of us every useful med has some drawbacks.

True callouses often disappear with continued wear/use, as most guitar players know. We start out with callouses on the fingertips, but as we continue playing the callouses vanish and our fingertips stay more or less normal looking and feeling. And while many folks who run or walk a lot -- including barefoot -- develop callouses, that's usually because they don't even try to remove the excess dead tissue. Take an exfoliant scrub bar to 'em and the callouses will vanish while the heels, toes, etc., remain tough. I've been jogging more than cycling this year and have some callouses on my heels, but that's only because I misplaced my exfoliant scrubber bar (looks and feels like lava) a few months ago and the Scotch-Brite pad I've been using doesn't work as well. I don't need callouses for my feet to be tough enough for running.

Long relaxing soaks in a tub with Epsom salts helps too. I'm heading to the tub for a soak right now.

Also, try Walgreens Moisture Barrier Ointment. Best I've found. I used it for my mom's bedsores as her condition deteriorated her final year (Alzheimer's and a bunch of other stuff that kept her in a wheelchair or bed her final year). I've used it occasionally when I had an ingrown hair or other irritation around my sit bones. Works great. It contains zinc oxide so it's very persistent and doesn't rub off easily, but that also makes it tricky to clean out of padded cycling shorts, etc. I use Fels Naphtha bar soap to clean out the zinc oxide (it no longer contains any naphtha, though, so it takes a little more hand work than it used to, but still works better than ordinary clothes detergents).