Relative cheated us and forced to sign

Hi sir, We have purchased a flat in podili andhra pradesh from our relative .he is my cousin.he said he is selling those flats for 20 lacks and he gives us only for 15 lacks as I am sister.apartment gets completed in another 6 months so when u resale immediately get 5 lacs profit.so we proceeded and given advance for 5.8lacks.for remaining amount we tried hardly for loan and coulnot get it.years passed.he regustered flat on us in 2013.but there is no progress in construction.he forced us to pay remaining amount.we dont have money so we said if any buyer is there we will sell it and give ur money to u.then he said he will return our money within a month and requested to register the flat for other person.based on relation and trust we have signed and given him back the flat in 2014 Nov 7th.tillnow he didnot return our money.and saying directly that he willnot return I can do whatever I can do.we have note with us on same date 2014 Nov 7th for 5.8lacks.please let us know what is best way to get our money back and he should be punished. Thanks Vasudha