@sreejan1508
To understand it better I will describe how this process works.
First of all Nextend Social Login doesn’t load images from external URLs. So, when a user registers with Nextend Social Login, we create a new WordPress account > download the profile image from the provider – e.g. the Facebook profile picture – > we store the image on your server as a WordPress attachment that is linked to the user that we created > by using the dedicated filters of WordPress we assign this image as avatar for the WordPress user that was just created.
So instead of the gravatar, WordPress will display the image stored by Nextend Social Login.
There are plugins/themes that could allow your logged in users to set custom avatars for themselves. WordPress has filters that developers usually use to modify values. So if you have a third party plugin/theme with custom avatar functionality that could override the avatars that we display.