Hystiocytoma questions

My 1.5 year old randomly had a small bump pop up by his mouth. I only noticed because he had been itching it and it started to bleed. I took him to the vet where they said it is most likely a hystiocytoma. They said they weren’t concerned it was cancer, and wanted to wait 1-2 weeks to aspirate it because it could likely go away. My question is, how long did it take for your dog’s hystiocytoma to go away? My dog has been wearing a cone to keep from scratching and taking an antibiotic. I feel bad for him, and felt worse when I saw that it can take 2-3 months to resolve on its own.