keep the lights off, or only light one side of the tank so that your O can relax in the darker side.
oscars have big personalities and they will sulk for the littlest thing. he's sulking due to the huge upheaval of his world right now. give him time, he'll come around.
one thing i found helped with my O when i got him was to give just the teensiest bit of food every time i was by the tank. this taught him that the big bad human gave yummy things, and now every time i pass the tank my O begs like crazy, lol. got him in spring of 2009. nowadays i can put my hand in the tank and pet him and even hold him still in the water. he doesn't mind one bit.