For those who lived during the time, how massive was Nirvana really?

I was born in the mid-2000s and became a Nirvana fan probably when I was around 13. I have heard from some people that Nirvana was pretty big, yet I heard from others that it was just another band that had no significance of pop culture during the time,

So really, from people who lived during that time, how massive was Nirvana during those days?