Liz Buchanan BVSc
Hello! Let's get under the skin. You appear to have a flattish, punctate lesion, with hair-loss around it. I can't tell the depth, putting it anywhere on the spectrum between a pustule that is drying up (spot - superficial), or an entry point from a cat bite-wound (deep). If the latter seems at all likely, your vet may want to give antibiotics right away, so check with them.
Assuming that it is superficial however, a cutaneous manifestation of cocci is highly possible. This would not be a diagnosis, but a consequence of something: perhaps some kind of insect bite that has caused a mild irritation / infection, for example, or a scratch that introduced some bacteria or yeast. It could, at a pinch, be ring-worm, so wash your hands after dealing with it just on the off-chance (low likelihood but take no risks). That may be an epidermal collarette around the outside of an infected follicle.
So what to do? If it is itchy and therefore getting scratched and getting worse, your vet should be made aware of the lesion relatively soon, as such lesions can quickly become much bigger. If it gets bigger and changes or is not better after the weekend, we would also advise showing this to a vet.