What is this?

I have taken my 7 mos old chi to the vet twice and she looked at him and said she has no idea. She took Archie to the back and got no help from another vet there. This happened over a course of two weeks. Vet said it looked like a plaque and tested a scraping. She said it’s not warts, cancer or tumors. Shot of antibiotics and inflammatory meds and sent home. This was 6 days ago.