Hi there Karan_19,
If all your contacts are showing the same photo, let's first check if this is only happening on your iPhone or if this is showing on multiple devices that you sync your contacts with. If you sync your contacts with iCloud, go to the iCloud website here and check if the contact photos show the same as your iPhone: iCloud
If you sync your contacts with another account, check the contact photos on their website in a web browser.
If the photos only show the same on your iPhone, that isolates the issue to the device. Go ahead and restart the iPhone and ensure it is fully updated. This installs feature improvements and fixes that can resolve unexpected behavior like this. These articles show how to do this:
• Restart your iPhone - Apple Support
• Update your iPhone or iPad - Apple Support
If the contact photos show this way on multiple devices, please provide more details on which account or accounts you use to sync contacts with and if you can manually edit a contact photo. That will help us isolate what's happening further.
Cheers!