How to block/unblock someone on Instagram?

If you are even slightly active on social media, you must be well aware of the social media bullying, i.e people commenting their ugly hearts out behind an internet profile. For some, the reason might be different, but 'block' might be one of the best features on social media platforms. You can block an old friend whom you no longer want to be in touch, or an ex or even your nagging relatives who are a bit too interested in your personal life. However, if you've blocked someone by mistake, or even if you wish to unblock someone, here's how you can do it.