I've not seen this before but most skin irritations are caused by fleas or allergies so those are usually the first things to rule out. The placement at the base of the whiskers is unusual, though so I'm hoping that your vet has an answer and a solution for you. Will you please let us know what the vet says? I'm very curious about this. It looks uncomfortable - does your cat scratch the spot? It's interesting that hair loss doesn't appear to be occurring.
Since this is your first post, and ! I hope you will take some time to look around the site - you'll find there is a massive amount of information here and a very warm, caring community. There are many experts here in cat-related issues, so hopefully, one will stop by with some insight into your kitty's problem.
Oh, ringworm. Yeah, I forgot to mention that. I'm sure your vet knows ringworm when he sees it, but you might consider asking to have a skin scraping cultured, just to be certain.
This thread deals with ringworm - it's fairly exhaustive and is very long because many different members contributed. If you aren't up for reading over 660 posts, do check out the first post. It gives a lot of valuable advice to people who have just had a cat diagnosed with this scourge.