I agree with Lacey - amphibians are much more difficult to successfully treat medically than snakes and lizards; often, once an infection is seen it is too late for them
We had a whites with a sore leg; we treated him with tamodine - a specially marketed watered-down version of iodine, used to treat human cuts and sores. It didn't seem to reduce his life quality; he was still able to climb, ate well and lived happily with our female whites for some time. He recently passed away, but I believe that more to be due to age, however, in this instance, particularly because it was a new shipment, it will be safer for you to keep him in quarantine until you can determine what the problem is.