Accidentally viewed child ?

Today I accidentally viewed a ographic image of a child while on a forum I go. The person who posted it was quickly banned and the image was removed. Unfortunately this was after I stumbled upon it. Now I know stumbling upon it is not an offense and normally I shouldn't worry. However I am a Law and Justice Major who plans on becoming a Colorado State Trooper. Will this incident cause me to be rejected? What will I need to tell them when I take my polygraph test? Thank you in advance.