Before running the nvidia installer from your command prompt, type and execute the following command line:
This is what he meant.
Details: when the installer will try to compile the nvidia kernel gateway module it will compare the version of the compiler you are using to compile it with the version of the compiler that was used to compile your kernel. It does happen quite a lot with mainstream distros that the compilers are different.
But the compiling process of the nvidia kernel module stops if they are not the same... so this environment variable(i.e. IGNORE_CC_MISMATCH) sets to "y" will bypass the test to allow you to compile the module even if the compiler versions do not match.