Hello and welcome to FF! Agree with other posts in that it looks like localized edema cause by infection. This frog needs a veterinary, possible drainage, and anti-biotics now. Also, be aware your temperature is to low and overtime it will cause permanent damage to frog's kidneys and lymphatic system.

One thing you need to do if keeping other frogs is too wash hands with hot water and antiseptic after handling this frog and it's enclosure. Do not let this frog share anything or get near any other frogs in your collection. Would transfer to hospital enclosure while you get visit to veterinary, good luck !