It’s called Phimosis @notasbad and it happens myself and @Simon_101 have issues with it. Please go see you Dr as soon as you can, they are likely to start you out with a cream or two to try to relax the skin to elastic ate it back to where it was.
The most likely outcome is a meeting with a urologist and the removal of the foreskin and that’s okay. I’d prefer to have a functioning penis than one that’s stunted from fully working properly due to being caged and stopped by that little ring of skin.
We have talked about it in other topics too “Cut” is one of them There are other topics of freaking or non on the forum too.
You are not alone and it’s not the end of the world 
