About The Cars

I have an 02 Es300 and on the passengers side i guess in the wheel well you'd call it there is a huge plastic piece that lines the inside of the well above the tire. This piece has fallen about 1/4 the way off and is rubbing against the tire, what is the name of this piece? How much does it cost to repair? And do I have to worry about any tire damage because I drove about 30 miles to get home with this problem? Thanks