bro lodge a complain on CM complaint portal, i am sure you remember the exact time date and their faces when this incident happen to you. just write the whole story. they respond very efficiently. Even though you paid them but those 500 will get that filthy police guy in real deep ***
here is the web address
:: CMS ::Online Complaint
Same thing happen with me at kala shah kaku interchange when i was entering motor way after pick a friend from airport, they said my car number plate is not computerized, but in reality it was 2006 reg cultus and it was registered before those Punjab no plates were launched. so after a long conversation one of the police guy said give them 500 rupees and they will let me go. it was 1 am midnight and i don't wanna get in more trouble so i paid them 500 and lodge a complaint against police officer with exact time and place. CM officer responded within 1 week and that police man who asked for bribe almost lost his job but eventually i ll have to forgive him because of some personal matters.