Especially if it's a older dog I would urge you to go in. Several years ago I thought my dog was having a repeat of a prior fungal infection he'd had in his sinuses and been treated for successfully by a vet where I used to live. So, because it was cheaper, I got the antifungal mister from that vet to save the cost of a new vet office visit to check it out. Same symptoms, like 2 years later, I figured the fungus is back and we'll dose it, and bam, done, right?
Wrong. The dog had sinus cancer which killed him about a year and a half later. I fucking loved that pup, and I quite likely passed up a chance to catch it early and maybe treat it effectively. I dunno, and it breaks my heart to think about it. Don't let it slip would be my take, although I get the $$ concerns. I'm never gonna feel OK about that.