Since, he's new in the tank give him sometimes to adjust to the new environment, and new things around him, let him settle down for a few days or a week. He'll calm down and less stress. Turn off the light for few days to see if he'll improve. It happens to any new fish the stress bar will disappear when the fish get use to it new environment. By the way, do not make any sudden move when you near to the fish tank as this can stress the fish even more.