[Closed] Grinding noise from brakes

Hi all - Disc brake Noob here looking for a bit of advice. I've got Hayes Stroker brakes fitted on my new bike. After riding today (3rd time out on it), the brakes are making a pretty horrible grinding noise when freewheeling, not when braking.
I did go through some pretty big muddy puddles so I'm hoping that it's just some dirt on the pads - just wanted to check that it was nothing more sinister.
Cheers