Construction wall ownership dispute

Dear Sir, My Native is Narasaraopet Guntur District AP State...In 2008 We bought a site with 4 boundaries...On South Side In My Registration Documents it is mentioned own wall....But adjacent owner tells it is a joint wall...that adjacent owner has no registration documents....but he is famous person in that area....Now in 2017 November we started construction...So,tell me in which way we fight against him...and what questions we asked him to proceeding legally.