My left Indicator is sticking on....?!?

Iv got a corsa.. 04 plate. and the left indicator keeps sticking on, the arm inside clicks off but the light on the dash stays on and they indicator light outside is on. (not flashing though..) Pressing the hazard light a few times turns it off. but does anyone know how to fix it?! Its ran the battery down once, as I didn't know that it was sticking. Thankks in advance!!!