Ahhh sweetie, you are not ruined. It doesn't really work this way. Our vaginas are made to stretch to 'accommodate' whatever it is that we are doing whether it is having sex with a large man or giving birth. It goes back for the most part. AND, there IS something you can do if you are worried (we should do it anyway). Have you ever heard of kegel exercise? This is exercise for the muscles deep inside of you. To figure out which ones, they are the ones you must engage in order to stop a stream of urine flow when going to the bathroom. By working those muscles, you get better control of the inside of your vagina and can tighten it at will. Here's some instructions: https://www.mayoclinic.org/healthy-lifestyle/womens-health/in-depth/kegel-exercises/art-20045283
you tighten those muscles and hold, then repeat 10 times. Do it often.
This should help. Don't worry though. Men are happy to have sex with a woman and the idea of being stretched out isn't really the reality most of the time. Truly.