Seeing as it happened one time, it was a cartoon, and you seem to have repented and don't have any consitant problem with it, I wouldn't think this is something you need to go to your Bish. about. But really that is a very personal decision. If, as you've prayed about it, you cannot seem to be at peace with yourself, by all means go to your bishop if thats what you feel you need to do to clear your conscience. Just my 2 cents.
Take care.