Rubbing of the rostrom is common in captivity, it is commonly associated with a highly abrasive surface in the tank (such as a screen lid) in combination with stress. You must first the thoroughly evaluate your set up and determine what has caused this animal to try so hard to escape that it rubbed the skin on its rostrum raw. You mentioned there were other frogs in the tank... are they of the same species and size? How many do you have and what size tank? Have you provided enough hide spots in the tank? What is the water quality like, how often do you change the water bowl?
Treatment involves applying a triple antibiotic ointment to the affected area with a cotton swab one to two times a day. Use only the generic, and basic formula of triple antibiotic, with no additives. If the frogs has to be restrained in order to do this, it is best to use moistened, powder free rubber gloves to prevent damage to the amphibians skin. Chances are it will probably have a scar or discoloration.
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*Humans aren't the only species on earth... we just act like it.
".the oldest task in human history: to live on a piece of land without
spoiling it."
Aldo Leopold (1938)