I am a 22 year old female and found a painful lump that looked like a giant pimple in the shower and it burst. It was just diagonal from my genital area, between my hip bone and my genitals. When I showed it to my mom she said it was an epidermoid cyst and that my dad gets them on his back. it was full of blood. it has a small opening now and I am worried about getting an infection. What should I do?

Summarized question: What causes epidermoid cyst?