In a more positive sense, if the 'giant cock' is a unique or special feature in the story, the moral could be about acceptance. Accepting one's own distinctiveness, even if it seems strange or out of the ordinary at first. But we should always remember to present it in a proper and respectful way, not in a 'nudity' sense as in being inappropriate.
Well, if it's a story, it might be about the danger of exposing too much too soon. The 'giant cock' could stand for some sort of power or ability that when shown naked (or fully exposed) without proper caution, can lead to negative consequences. For example, if it's a power that should be used subtly, being too blatant about it can make others feel threatened or envious.