My rear camera's lens have gone blur cuz it fell once.

Since you have three cameras on the back side of the phone and two of them are working, it seems fairly sure that your camera sustained some sort of damage in the drop. Although it wouldn't hurt to check, it's unlikely the camera just came unplugged from the fall; like most phones yours has a midframe plate that holds all of the components and connectors firmly in place so that's a problem we almost never actually see.

So the most likely fix for your camera problem would be to replace the camera. I wasn't able to locate a written guide for the 10 Pro 5G, but there is one for the 10 Pro; the procedure should be similar enough to get you through the repair. Note the guide is written in Spanish but used with the Chrome browser's translation feature it's quite usable no matter what your native language is.

Manuals / OnePlus 10 Pro / Rear camera - Nobody Calls Me Chicken

You may have to shop around to find a replacement part specific to your phone; be sure to check your model number against the listing to ensure it's the right one. I'd suggest starting with Amazon, eBay and AliExpress, but there are undoubtedly many other sources such as this one.

OnePlus 10 Pro 5G Rear Camera Replacement Module - Cellspare

Of course you'll want to try all the software solutions first, such as restarting your phone, perhaps even restoring it to factory settings (after backing it up, of course), but if those fail then replacing the camera is the most likely fix.

Good luck and let us know what happens!