“Popping the cherry” is a slang term for tearing the hymen, a piece of tissue that’s partly across the inside of the vagina. It usually stretches/wears away during childhood from activities like bike riding and gymnastics. If the hymen hasn’t stretched/ worn away and someone has vaginal sex, it might partially block the partner from entering the vagina. If the sex is forceful, it can tear, causing bleeding and pain. Because the hymen is flexible, it doesn’t always tear from first sex.