Customer lodged fir against bank and the manager got clean chit

I am clerk in govt. Bank. There was incident happened in may2016. A customer issued a cheque to someone and his cheque was chemically altered and cheque was cashed on the counter. Payment is made in due course. Customer has lodged an fir in Aug2016. And in internal bank enquiry and vigilance enquiry, the manager who has passed the payment is free of charge. There is negligence but banker's intention is not involved and he has retired and got clean chit. I am the clerk who entered the cheque in the system as cheque was apparently normal. Now, I am getting call from police officer. He is trying to scare me to compromise on the basis well known to him. He is saying me that I am involved in this case, and if I won't agree to his condition, he would arrest me. And I need bail. And he is giving me 10 days to answer. Please tell me what should I do? Can he make arrest? If case is filed than it will be against bank or individual? Please reply