You do but you have also relinquished all rights to Instagram to do whatever the wish with.
This license grant means that you have given Instagram the right to use any of your photos for free for pretty much any reason anywhere in the world.
You can report if someone is infringing on your published pictures.
Last know Instagram link for filing copyright on your pictures by a party other than Instagram.
In this day and age information is pretty much free because of the volume of information that is getting blasted on the web every second by billions of people. Somebody will become a nobody and nobody will become a somebody every second. It is a tidal wave of confusion so good luck chasing people that have used your content. Just keep making more great content and let the other stuff go.