That is always a possibility - hence the reason most folks recommend you quarantine all new fish before adding them to the pond. But in any case, that damage is already done if it is infected. Removing it now is closing the barn door when the horse is already gone.
However, my money is on the fact you just got a sick or weak fish that's having a hard adjustment to the new environment. It may or may not make it through the transition. Did you acclimate the new fish before adding them?