There is a steel plate behind your brake roter. ITs thin maybe 1/16'' I'm willing to bet when you changed your brakes or cv boot, or maybe even just rotated your tiers you bent the plate in. Its just a heat deflecter. Take a screw driver and pry it inbetween your roter and the heat deflecter tobend ther deflecter away from your roter. Just be careful not to score your roter.