I'd had something like that, but hadn't waited as long as you. After about 5 months I went to an ENT who said it was probably a staph infection (no idea how I got that, but I had a surgery where they probably shoved a tube down my nose, so that's probably how). She told me to apply one of those zinc based antibiotic ointments. That somewhat worked, but the bump kept coming back. It never fully went away until I started flushing my sinuses with Iodine treated water. I bet yours was also some sort of infection, and the SSKI killed it.