I found a little black rock/ shell looking object on/inside my back! Creature laying eggs inside me?! HELP!?

I am 15 years old and i'm a male. Ok so i have been having this pimple on my back for like about 2 weeks now, and i decide to pop it because it was getting bigger. After i squeeze i see this huge black thing come out so it wasn't a pimple, i observed it closely and it appears to be some sort of a shell or something, It feels like a rock, but when i used some mini pliers to try to open it a little, some gooey substance is inside. WTF is this? I am soo scared that this might be serious. I covered up the hole on my back with disinfectant creme and alchohol, and with a bandage. I asked my parents and they said it might just be a rock i layed on but i am too paranoid right now. I provided pictures of both the shell/ rock and how my back looked when i removed the object. Please help!