What's wrong is that the hard drive is damaged an the computer can't boot off of it, that's why you're seeing the question mark.
You'll need to get the hard drive replaced. Apple probably will fix it, but they'll charge an absurd amount of money considering that it's a fairly simple task.
Here's a link to a guide on how to do this:
https://www.ifixit.com/Guide/MacBook+Pro+13-Inch+Unibody+Mid+2012+Hard+Drive+Replacement/10378
You can buy hard drives for pretty cheap. Around $35 for a 500Gb one to about $60 for a 1Tb one.