Legal Suggestion Needed : Comment

I Purchased a piece of Land about 8 years ago from one of my friend. After that, i built my house on that piece of land and start living peacefully. Now the issue is that in good faith, ‘registry’ of that land was not done ( Ownership was not transferred to me) as he the seller was a know person to me but i had paid all sum of money to him at that time which was demanded by me for the land.

Now today, he is blackmailing me that the ownership of land is on his name, so either again give money for that land on today’s rate of leave the house. I have my house from last 7 years on that land as i had paid him the price 7 years ago but now for  registry of that land, he is demanding money from today’s increased rate.

What should i do now?