[Help] I have a disc problem

So, hi.

Many weeks ago, I posted a help thread wanting to know if my GTA V save file would vanish, since I erased the game accidentally. Today I decided to re-insert the disc and install the game again. But of course, there is a problem.

I inserted the disc, waited for the game to install, it came round to 25% and... an error message pops up.

It says "Cannot continue using the application. The disc cannot be read. Make sure that the disc is not damaged or dirty." The only option is [Close Application and Remove disc].

I checked the disc, it is fine, although I may have got something wrong.

Any advice?