Just remove the wrong tag. Tag = category
I have heard that you can't remove or change the first tag.
Even if you could remove the entire post from steemit, it will stay in steem blockchain. You can't remove it from there.
https://steemd.com/ is steem blockchain.
Thanks... that's sort of what I figured. Could not edit first tag... Oh well, it'll sink into oblivion soon enough. :)
I would suggest that if you use nsfw tag, put it as a first tag because that tag is shown in the "new posts" feed. That way people will know about that without opening the post.