Well yes, if the version numbers do not match, then you've got a slightly different kernel source than your running kernel is. Yet you haven't done anything dangerous, since installing the kernel sources means, as far as I know (the rpm-installation), installing the source files in a specific directory on the system. You can safely remove the package thus removing the source files but not affecting anything; the thing is, if you would compile from that source, you'd get a kernel of different version (in this case a newer one; that shouldn't be a problem).
If you're installing nvidia drivers then you shouldn't need to recompile your kernel; at least this far it has just been a matter of downloading a .run file that compiles it's own nvidia kernel module and installs it to the kernel. You need the kernel source code only if you plan to recompile your whole kernel (ie. if you want to alter the kernel configuration), but if you're just installing video drivers that's not needed.
You don't need to remove the kernel sources if you don't want to do so. If the nvidia installer requires you to have your kernel sources, then you need to install the same version of the sources than your current kernel is (so the version you get from uname is the same as in the package you installed). You should be able to have multiple kernel sources installed at the same time (but I don't know if that's of any use for you).
If you don't need the kernel sources, just let them be or remove the package as you'd normally remove a package (of some application, say). If you do need, you can remove the package if you like, but before you go installing the driver, get and install the sources of your kernel's version or update your kernel to the version of the sources.