If you can afford it take your iPhone to an Apple Store or contact Apple Support and start a service request to have your screen replaced with a new OEM screen. Apple charges $79 with AppleCare+ or $109 without AppleCare+. If you're more concerned about cost, find a reputable repair service in your area.
It's depends on which place you repair your phone
Apple store is the most expensive, and then is take your phone to the local repair store,
The cheap way is you buy screen online and repair it yourself
If you choose the local repair store or yourself ,you will voited your warranty.