If your the rpm file is in your home directory and your home directory is on NFS, root may not have access to it. This is somehow unusual: normally, root can access every file. But in common setup, when root access a directory that is mounted over NFS, the rights of the user
nobody are used instead of the root user. The main purpose is to ensure that root on the client cannot manipulate files as root on the server. This is implemented as “root has the permissions of nobody” rather than “root can have anybody's permissions execpt root's” primarily because this is easier (though there can be other reasons: some NFS server apply this to users other than root, so as to protect all system users on the server).
If this is the issue, you need to make both the rpm file and the directory containing the file accessible to root. That means making them accessible to the user
nobody, and usually the only way to do that is to make the file and the directory world-readable. More precisely, the minimal permissions are
chmod a+x .
chmod a+r something.rpm
Alternatively, move the rpm file to a local directory.
mv something.rpm /tmp
sudo rpm -i /tmp/something.rpm