Hello and welcome to FF; I'm very sorry for the frog . First thing to do is set it up in a hospital like enclosure. The substrate will be damp (dechlorinated tap water) unprinted paper towels (changed every 2 days) with couple branches and some silk foliage to make him feel safe. Also include a water dish with dechlorinated tap water cleaned with hot water and refilled daily.

You can apply any plain (not analgesic) antibiotic like Neosporin; Silver based; or Baytril with a Q-tip to affected area 2x daily. It's OK to medicate with frog asleep. If you need a herp vet, this should help locating one: Arav and Herp Vet Connection. Hope this helps and good luck !