Do you have a kernel-source package installed? rpm -qa | grep source to find out.
If so, you probably have to configure it to match the running kernel (or, it is also possible that the version of kernel-source that you have installed doesn't match uname -r). If you have to configure it, cd into /usr/src/linux-<whatever version>, then find the config file under configs/ that matches your setup, cp it to ./.config, and run make mrproper oldconfig dep. Then cd to the nVidia kernel directory again, and run make clean and make.