cracked MacBook screen

Hi everyone.

About a month ago, I noticed hairline cracks on my screen. There is not point of damage and I am extremely careful with my MacBook. It has a case on it and I never throw it around or place it where it could be damaged. This crack came out of nowhere. I did NOT set it down too hard or put it in a dangerous place. It was simply sitting on the floor AWAY from anyone or anything that could damage it. And no I did not set it down too hard. A couple of days ago I opened my laptop and now there as green lines coming from the hairline cracks. When I run my finger over the crack, though, I can't feel a crack leading me to believe it's not on the surface. I need to know how much this will cost me to fix.