One way a person promotes themselves on Tumblr is to follow your account. Its no different than any other social media platform. People will often visit your follower list to see if there are any other interesting blogs.
1 – Sing into your account.
2 – Go here https://www.tumblr.com/settings/blog/. The URL should auto update to include your account name on the end of that URL.
3 – Go to the section ‘Blocked Users’
4 – Click on the pencil icon to edit the list.
5 – Add the user account name you want to remove from your Tumblr account.