My art has been stolen/recolored. Help?

iconosquare.com/p/828492925404…
Soo, I came across this on instagram.
It's been recolored from this:


I only came across this one by coincidence, so I'm worried if there's others I don't know about? The same user has also used one of my pictures in a video or something - I don't mind that so much, but I don't really like my art being recolored.. But they've also recolored some other art I recognize too..
I'm honestly not sure how to go about this because it's instagram of all sites. Advice?

EDIT:
So the artist took down the image. Nobody contacted them before this, meaning the user has seen my journal (as I've come to realize that they also watch me on dA, so I know you're seeing all of this, as you were also online when I posted this journal and immediately took the work down right after.)
So that's done.
However, the work recolored from me is the only image that was taken down. So, there are still several images stolen and recolored on there. This tells me the user simply didn't want to get in trouble since I caught them. And instead of apologizing to me or anything, I come across this:

Wow.
Just because others do it does not make it okay.
That artwork is not yours.