The teen's aunt and guardian, Stacy Bigley, said police had a warrant to take the pictures.
The teen faces felony charges of making and possessing child pornography.
News of the plan to take the photographs sparked a furor on the Internet on Wednesday.
Flores Laboy and Bigley said that police photographed the teenager's genitals last month but wanted the additional photos for better comparison to their evidence. In order to make his penis erect, they planned to take him to a hospital and give him an injection, Bigley said.
The Manassas City Police Department said in a statement Wednesday that it's not its policy "to authorize invasive search procedures of suspects in cases of this nature and no such procedures have been conducted in this case."