Once you block a user on Instagram they cannot view your photos or search for your Instagram account. Users are also not notified if they become blocked.
To block a user first locate their profile page and then tap on the gear icon in the top right corner of the screen. By tapping on Block user a user will no longer be able to view or search for your Instagram account.
By default anyone can look at your photos. To ensure that only followers can see them tap the Profile tab, find the privacy section, and then switch Photos are private to on. Now only people who have a friend request approved by you will be able to see your photos.
Instagram’s newest update, 3.0, has a new feature called Photomaps which pins your geotagged photos on an interactive world map. Maps are turned off by default. You can also display photos in a 3-across grid and enjoy a larger text box for your captions. Infinite scrolling loads as you go and spam and abusive comments can now be deleted and reported at the same time.