i noticed a vertical line in my thumbnail a few months ago and was hoping it'd go away. about a month ago, i noticed it had cracked! now there's a split that i'm hoping will grow out but no matter how much i file the vertical line down the center isn't going away and i feel like the nail is doomed to split when it it's the breakign point near the top of my nail!!!

any experience? how to fix it?!?!?!