Sodium present in diclofenac sodium has any relevance with sodium present in our household salt or it is in some other chemical form?

No: Diclofenac sodium is the generic chemical name for Voltaren. Many prescription medications are chemically in the "salt" family but do not have the same effect on your body like household salt. You need to pay attention to the the diclofenac (active ingredient) and ignore the "sodium" part of the name in order to understand how the medication will affect your body.