Your crack is in an area that is pretty common - close to the hinge, where it doesn't take a very large object to apply a lot of pressure when the lid is closed. It's related to the MacBook being very thin, not much clearance for any kind of object around that hinge area. Then, you open the lid, the object (whatever it was) slips out, and you may not even realize that anything was left in the wrong spot - and now the screen has cracked.
There's only one fix - and that means getting the screen replaced.
A cracked screen will usually be considered accidental damage, and can be replaced by using an incident on your AppleCare+. Screen damage would be a $99 charge.
If you don't have AppleCare+, then it would be a lot more.