The screen is broken and has to be replaced. I'll give you my standard line here - DON'T try to save money by replacing it yourself. It'll cost more by the time you're finished fixing everything you break than if you pay a shop to replace it for you.
BTW, a 12" drop, done "correctly", can shatter an LCD internally. If you really get it right, a 6" drop could probably do it. Conversely, dropping the phone just right, 3 feet onto concrete, can leave it unscratched. It's like the difference between a bullet tearing through the left side of your shirt, or just 4 inches to the right, through your heart. It's just 4 inches. If it passed anywhere to your left, within 50 miles, you'd be fine. Just 4 little inches. It's the same with the screen. Just the right shock, to just the right place in the screen, kills it. The same shock, just an inch away, or a few degrees different, and the screen is fine. (Keep the phone in a TPU case, at least, to give it some shock resistance.)