Hi, this is not Apple Support. Apple and Apple Support do not participate here. Everyone posting and commenting are fellow Apple users, just like you.
Have you tried a forced restart? It’s known to fix many screen related issues.
Force restart iPhone - Apple Support
If that does not resolve the issue you need to have Apple perform diagnostics on your iPhone. It can be done in person at an Apple Retail Store or at an Apple Authorized Service Provider. You can also contact Apple Support and request remote diagnostics.
If you’re in the US, please call 1-800-MY-APPLE, or outside the US, consult the support articles below. In Canada, call 1-800-263-3394.
Contact Apple for support and service - Apple Support
Genius Bar Reservation and Apple Support Options - Apple
Explore Service Locations