Your options are (1) just keep the flight up to DEL, (2) cancel the ticket, or (3) ask AA to reroute you to a different airport such as CCU (e.g. if 6E's CCU-IXR flight is more convenient for you, or if you are going somewhere far from Ranchi which would also be accessible from another airport). It sounds to me like the first option is probably as good as any.