Kind of surprised how little it sounds like the vet did too. When i took Rosey in for the sinus infection, my vet took a sample of the goo from the lump in her nose and from there Id'd it as a bacterial sinus infection. Also looked inside her mouth to make sure it didnt eat through the flesh into the mouth area i guess. Not exactly sure as I am not a vet but i guess sinus infections can spread into the mouth and bone etc. She said everything looked good for what it was and gave me the month worth of Fortaz shots. She then told me, if i was scared or worried about giving shots, i could bring Rosey in every 3 days with one of the shots and a nurse would give it to her for me but i was fine doing it myself as Rosey is big.
If the vet just looked at it and said 'meh' more or less, i would have asked them if they arent going to do an x-ray or at least take a sample of the lump to see what it was. I think, you need a new vet and a second opinion. Just my opinion.