Vet says he has Tumor but I'm not sure

[FernFellow]

Went to the vet the other day after noticing one side of his mouth was swollen. They said it was a tumor (he's 11 btw) and that because of his age they said it would be a waste of time to operate since it would come right back. And suggested euthanasia. I asked if we could try anti biotics first, they said sure but that I should be ready to come in and put him down once it gets bigger. Today I noticed that it just doesn't look as big as before. I can't get him to open his mouth right now to get a picture of the mass but I do have pictures from the other day. Does this look familiar to anyone as to what it could be? I don't think it's a tumor but the vet I went to was experienced. Honestly I'm just scared and don't want to loose my buddy.

 

[FernFellow]

 

[FernFellow]

 

[mango_the_beardie]

View attachment 67956

ok so to me that definitely does look like a tumor but if it seems to be getting smaller than in about 3 days can you do me a favor and take a picture again bc unfortunately my beardie also died from a tumor and in the span of 3 days it was 5x the size so in 3 days I'll definitely be able to tell.