Please do not use Peroxide as it can irritate the tissues. I suggest using a diluted Betadine and water solution and clean, followed by using some Neospirin.
The Water Dragon should see the Herp Vet for an antibiotic and to make sure no further problems occured. Make sure you clean the wound area at lest 4-5 times a day.
For feeding you can make a slurry of chicken or beef flavored baby food stage 1 mixed with some calcium powder and feed. This will help with nutrition. Make sure you clean the wound area at lest 4-5 times a day.
If you do no not have a Herp Vet, please supply a State and I can locate one for you with a State.