That's in the tail- below the snake's cloaca (aka 'vent') so it's NOT normal & likely to be an infection/abscess, or a tumor- yes, you do need to see a vet for this as soon as possible. If you need to find a qualified herp vet, try this link (in the USA): https://arav.site-ym.com/search/custom.asp?id=3661 Good luck, & let us know how it goes?