no more direct torso exercises, of course. choose exercises that require as little abdominal stability as possible. no more squats, deadlifts, military press, chins, etc. over a long period of time (months, years) that could work.
or stop lifting and eat less and lose size everywhere. that would work, but im sure it's not an option.
it's your symmetry and genetics. besides, you probably look fine and are the only one who sees it.