Do you have a herp vet locally? How long since the bite occurred or was noticed?
Quarantining in a "hospital cage" is a good idea to prevent further wounds and stress from cagemates.
You may be able to manage this wound with a topical antibiotic. A generally accepted procedure is to move the newt to a smaller, treatment container with a simple substrate of dampened paper towels, apply the treatment, wait 10-20 minutes, then gently rinse off the agent and return the newt to his hospital tank.
I've had a lot of success using silver sulfadiazine (Flamazine) cream, but this is by prescription only. If you are really stuck without a doctor to consult with locally, you can also use any over-the-counter ophthalmic antibiotic ointment. Most commonly you will find one that is bacitracin/neomycin/polymixin or other similar mixes.
Be sure not to purchase an ointment that includes a steroid (i.e. hydrocortisone, dexamethasone, etc., can't remember which ones you will find readily in OTC ointments). You do not usually need a steroid in infected wound management, and they can cause more harm than good when used inappropriately.
With the OTC antibiotic ointments, you can apply a small layer to the affected area with a cotton swab/Q-tip once daily, and hopefully you will start to see improvement within the week. I generally continue treatment until I see a nice layer of granulation tissue forming, the skin will look more intact but still a little pinkish or whitish.
Try to keep the little guy eating during the treatment period. Reasons for him to not eat could be stress (change in environment, wound pain), pain, or he could be septic. Stress can hopefully be avoided by providing an accommodating enclosure that is similar to the permanent enclosure. Pain management needs to be addressed by a vet. If he is experiencing septic shock from the infection spreading systemically, he'll need some severe intervention.
Keep us posted.
