If your Instagram account is set to private, you can remove people from your follower's list anytime. As you remove followers, they won't be able to see your posts in their feeds. And neither they will be able to see your posts when they are on your profile page. Removing them from your list will hide revoke their access to your posts.
Here's how you can remove Instagram followers:
- Go to your profile
- Tap Followers at the top of the screen
- Tap to the right of the follower you'd like to remove, then select Remove
- When you remove a follower, they aren't notified that you've removed them.
You can also block someone to get them to stop following you. People aren't notified when you block them.