1-Log in to your Instagram account.
2-Now click the navigation panel on the bottom right corner of the task tab of Instagram. Now click search on the top right corner of Instagram.
3-Now search for the User whom you want to unblock by typing their user name.
4-You will get a list of Users. Choose the ones you want to unblock.
5-Now on the User profile click on the top right icon to get options.
6-Now you will get a menu for unblocking the user. Click the unblock button.
7-You will be asked for confirmation for unblocking the user. Confirm it. You will get a message stating the user has been unblocked.
hope it helps
take care ,