Garter snake has a lump on its side?

[okay]

Hi I'm new here sorry if I'm using this page incorrectly but I don't really know what to do lol. I have a garter snake that's about 2 months old and it developed some sort of small growth under its scales, not quite on its tail but pretty close. It is on a diet of Night crawlers and Red rosy minnow things. Something that concerns me is one of the minnows tummy was very large and after keeping it in a separate bowl for a few days a parasite (a small red worm-i forgot the name) came out of it :-( yikes i wont be buying from that store again. But I don't know if i missed another infected fish and my snake ate it and got a worm as well (i don't know how that works)? Or if its an abscess? its been about a week if not more and i think it might have grown? Im very worried I don't know what to do and I'm not sure if my vet will see snakes. Any help is certainly welcome, thank you