Whoever told you that information has a highly vivid imagination.
There is no internal anatomy which is changed or which "pops" during first intercourse.
In most women in their teens, the hymen has at least partially eroded on it's own, due to regular physical activity, tampon use, or just the passing of time.
First intercourse hurts for some women, and does not for others. For some, that pain may occur more than once.
Have a read here for more: http://www.scarleteen.com/politics/virginity.html
Editor and Founder, Scarleteen
My epitaph should read: "She worked herself into this ground."
-- Kay Bailey Hutchinson