For example, liquid damage isn’t covered by warranty but might be eligible for out-of-warranty service. If your repair isn’t covered by Apple’s One Year Limited Warranty, AppleCare+, or AppleCare Protection Plan, your iPhone might be eligible for out-of-warranty service. Pricing and terms vary for service through an Apple Authorized Service Provider. The final service fee we charge will be determined during testing. IPhone 6 Plus, iPhone 5s, iPhone 5c, iPhone 5 Accidental damage isn't covered under the Apple One Year Limited Warranty. If it has, or if it needs other repairs, you may need to pay an out-of-warranty service fee.

Apple will run a diagnostic test to determine whether your iPhone has experienced additional damage. Repair and replacement costs depend on your iPhone model and your AppleCare product coverage. If the damage goes deeper, you'll have to pay the Out-Of-Service fee, to get your device replaced by a working unit. If you're lucky, Apple only has to replace the screen. If this does not work, the problem has to be hardware related and you'll have to get it serviced. Use iTunes to restore your iOS device to factory settings - Apple Support

If this does not help, setting it up as new device would be the next step: You will not lose any data by resetting, but it can cure some glitches. Try to reset the phone by holding the sleep and home button for about 10sec, until the Apple logo comes back again.

Iphone screen black and white stripes