Proximity sensor issue while in call

Hi, utsav49 and welcome to the Apple Support Communities. We'll be glad to assist you with your iPhone screen.

Are you referring to the screen remaining black when pulling the phone away from your ear? If this is what is occurring, please begin with the following troubleshooting steps:

1 - Quit the Phone app on your iPhone with these steps: How to force an app to close on your iPhone, iPad, or iPod touch

2 - Restart your iPhone & test again. 

3 - If the issue persists, go to Settings > General > Software Update and see if there are any available. If you find you need to install the update, first backup your iPhone with these steps: How to back up your iPhone, iPad, and iPod touch. 

4 - Update your iPhone, iPad, or iPod touch & test again. Be sure to try with both incoming as well as outgoing phone calls.  

If the issue persists be sure to message back with the results of the troubleshooting.

Cheers!