Which libsepol do you currently have, if any?
$ rpm -q --qf '%{NAME}-%{VERSION}-%{RELEASE}.%{ARCH}\n' libsepol
libsepol-1.11.18-2.x86_64
libsepol-1.11.18-2.i386
Try:
# yum update libsepol
See if that works, and if so, retry your yum install kmod-nvidia.
it works now , thanks : )
hicham.