Cleaning up your /boot partition
/boot partition will become large, and near its limit. This is often caused by old kernels being left on your system. The following steps should help to get that cleaned up safely, and hopefully reduce the size of your boot partition. This will keep the latest two kernels on your system, and remove the others.
Do the following to keep just the last 2 kernels on your system, to keep /boot clean
/etc/yum.conf and set the following parameter
This will make your package manager keep only the 2 latest kernels on your system (including the one that is running).
yum install yum-utils
Clean up your old kernels
package-cleanup --oldkernels --count=2
All done! This will erase (in a safe way) the old kernels, and, keep just the last 2 of them for future use or rolling back if necessary at a later date.