can admins of a website use django admin panel in production, or should I build one?
Yes, I would consider the Django admin a production-suitable facility for managing your site. (We rely upon it extensively.)
However, this does not mean that you don’t ever need to build some admin facilities yourself. The Django Admin is not the “be-all” - “do-all” solution that some people would like it to be. There are whole categories of administrative-type functions that would be better suited to a custom-written interface.
I always suggest people read the first two paragraphs at The Django admin site | Django documentation | Django and take that message to heart.