Hi, looking at the issue you have, it seems to me like either you deleted the kernel and didn't reinstall it properly, in which case the solution would be:
1-Boot into a Live CD of Cent OS
2-Chroot into the existing Filesystem
3-Reinstall the kernel.
The option 2 is that you installed a new kernel but the system believes that it is supposed to be using a previous version, in which case, the previous kernel doesn't exist and and needs to be installed.
Finally option 3, you modified grub but forgot to run the update-grub/update-grub2, depending on the grub version.