Refusing By Nephew To Withdrawal Of Joint Savings

My self and my nephew jointly purchased 26 No's of NSC certificate from Post office for a value of RS 10,000/- each, but after it's maturity my nephew after several request refusing to come to post Office to get release / withdrawal of the joint savings , please suggest me which Civil action I will take to get my money back and can I ask direction from the Civil Court to order the Post office to release 50% of my share in my favour.