Dark Splotch on Kole Tang

[FishStarter89]

I just bought a Kole Tang yesterday and it's currently in quarantine. At some point within the last few hours, it has developed a dark splotch above its eye under its fin. I have attached a photo. Does anyone know what this could be or what I can do about it?

 

[54seaweed]

almost looks like a bruise from a finger as pet shop held fish in net to prevent jumping till he was bagged , a lot of places put there whole hand over nets with big fish some grasp fish