Could be a bacterial problem or the result of a scuffle with another fish. If new, it could also be from netting. Best suggestion is a few water changes with well mixed and settled SW
and fortify the foods with some Zoe for the next week. After the the improved feedings and water changes, if there is no improvement after a week, you may need to QT
and treat. Hopefully that will not be needed.
Keep watch on the "spot". It could be an oddity or possible parasite. If it goes away after the water changes it's all good. Might just be a slight nick.