You have a warped brake rotor. Or warped drum if you have drum brakes in the back, or an off-center drum (too big centering hole).

You can get drums and/or rotors machined at your local auto parts store for about $10 each. But you need to take them off and put them back on. If the rotor is too thin, you need to buy a new one. Get the premium rotor - not the cheap one. For quality, make sure it's made in the USA or Canada. Just trust me on that.

Your brake rotors are warped; you can buy new rotors at $20 each from your local auto parts store.

You'll need to jack up your car onto jackstands, remove the wheel, remove the brake caliper, and the brake caliper mount to remove your old rotors.

Then use torque wrenches to bolt the parts back together again.

Good luck!