Hi, this looks like one of the radiator shrouds, it should sit between the radiator and the grille to direct the air into the radiator. This is not a critical part in the UK as our ambient temperatures are not as high as other markets the car is sold in, but it may cost you some fuel efficiency as air will be flowing through the engine bay, causing drag. I believe to be able to refit this, the front bumper needs to be taken off, and it is mounted using push clips.