ANTI POLLUTION FAULT?

i HAVE GOT A PEUGEOT 206CC, AND YESTERDAY WHEN I WAS WAITING TO PICK MY PARTNER UP "ANTI POLLUTION FAULT FLASHED UP ON MY DASHBOARD AND NOW THE ENGINE MANAGEMENT LIGHT IS CONSTANTLY ON, PLEASE CAN SOMEONE HELP ME WITH THIS OR TELL ME HOW I CAN FIX IT (PREFERABLY WITHOUT GOING TO PEUGEOT) THANKS