Yes you can!
For whatever reason you wish, to block another user from accessing your profile, log into your account:
Open the profile page of the user you wish to block.
On the profile page, you will see in the menu 'BLOCK USER'.
Simply click on 'Block user' right ON THIS TAB and the user will automatically be blocked from getting to your profile.
You can consult a list of the users you have blocked in 'Edit Profile' below your username on the top right of the page.
Select the 'Block List' tab to consult this list.
To unblock a blocked user, there are two ways to do it ; consult your block list and simply click 'Unblock User' next to the user you wish to unblock or go to the user's profile and press on 'Unblock User' in the 'MENU' section.