What can happen to you for getting caught with a fake id?

I am 17 years old live in australia and i decided to go to a nightclub with my 18 year old mates on the weekend. I don't exactly have a fake id i just have one of a guy that is actually 18 that looks like me. So anyway i went up to the bouncer and hes like id and im like yeah no worries showed him it and he said this is hard to tell its you man whats your middle name i told him its Adam and he said what star sign are you? i said aquarius, then he said sign your signature three times for me and i was really scared like shaking and stuff i had already practiced it and did it right. Then he said you know this is really hard to tell its you you need a new id mate. He then let me through but it worked easily at places in the city of Melbourne and this was just a nightclub in a suburb. What can happen to me if i get caught with it?