small red spot on golden barb

[E.R]

as I went to check my tank this morning I noticed one of my barbs has a small red spot on it. I have no idea on what it is and I have no clue on what to do. Please help im not as experienced as most and I have never run into a problem like this.

I have pictures now

 

[Delapool]

Hi, anything sharp in the tank or anything that could of attacked it? After that I'd check water chemistry (nitrates) and it looks like under a scale has gotten infected and a sore has resulted. Temp matched water changes every week and may heal on by itself, else I'd treat for a bacterial infection if not healing or getting worse. To heal by itself the water needs to be as clean as possible (low nitrates and organics).