Looks a little stressed on the left side. They sometimes will retract but not to the point where tissue is lost. Is constant flow hitting that one side?
Agreed. Looks stressed from maybe a sting of coral touch. If it is new, could be damage in shipping. Keep a close eye on it. If has any gelatinous stuff, get out and treat with antibiotics. Otherwise, make sure it is not getting direct or heavy flow, nothing stinging it or picking at it.