Maybe the display just went off, As you had dropped it and there was a visible crack as well call it an after effect. So its very convincing that if anything weird happens to the device all of a sudden that drop is the reason for it. The shock rattles the device and could cause instant visible damages while other could pop up anytime in future.
You need to take the device to the authorized service center for an inspection they would give you the impression on how deep the damage is.
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