Back of caliper grinding inside of rim

If these are stock rims about the only way that could happen is if the caliper has come loose, either the mount or the guide pins have let the caliper shift. Needs to be repaired ASAP because the caliper could catch and break the rim apart and cause you to lose control. This might help you determine which parts are the problem:
https://www.2carpros.com/articles/brake-caliper-replacement

Okay, from the video it looks like the pads could be worn out and letting the caliper slide out too far. If you look into the slot at the rotor and the pads themselves how much friction material is left on the inner pad? Hard to see from the angle but it looks like the piston is extended pretty far. I would also look in the rim and see what is actually rubbing, I have seen wheel weights that are stuck on that started to fail, but usually those just get torn off.
Thank you for the video, if you have a chance, you could shoot a few pictures straight onto the caliper so I can see the rotor and pads.