Could be a rear axle bearing. Much more likely to be a bent brake shield touching the rotor, or less likely broken brake pads scraping and damaging the rotor. Other possibilities include broken emergency brake parts inside the drum, or a broken c-clip holding the axle into the differential so the only thing keeping your axle in is the brake caliper, or something like a rock caught in the brake assembly. Everything should show signs of scraping the rotor, inside or outside, so I'd get the wheel off and if you don't see anything, remove the caliper and then the rotor and keep looking.
Or if you're not a mechanic - get it to a specialist.
Or if you're not a mechanic - get it to a specialist.
