The first step in blocking a user on Pinterest is to find his profile page. In the search box at the top of the Pinterest website, type the person's name that you are trying to block, and hit enter. If this person is following you currently, his name appears in the auto-generated list as you type.
Once you are on the person's Pinterest profile page, look at the top right corner of that page, click on the gear icon and choose Report from the drop-down list.
Click on Report at the bottom of the pop-up box. A confirmation pop-up appears asking if you want to block this pinner. Click on Block Pinner to complete the process.