open sore on mandarin

[scarpenter]

I have a mandarin that we put in our tank about two weeks ago. After we put him into our tank we noticed a small patch near his tail that was very washed out. He seemed to acclimate well and was eating, etc... Now a week and a half later that washed out place looks like an open sore or deep puncture wound. There is nothing else in the tank. Today we noticed another place. What is this and how can we treat. I can't get him to stay still long enough for a pic but picture a really nasty open canker sore.....

 

[bwest]

Hopefully someone knows what this could be, keep trying to get pic. From my understanding, it would be hard to do anything for it other than make sure it's eating and water parameters stay steady, since medicating the fish can actually hurt it more.