Grooming: Ever stuck a bandaid on your arm, then when you go to remove it.
Sticking a bandaid on your genitals is not natural.
Clean the area well with a baby wipe and then, just to be sure, do it again.
The game manually does not allow the Sims to be naked to make the game appropriate for all ages.
But where is that exactly? Stand naked with your legs together and look in a mirror.