Enforcing Sale of Plot by Joint Owner

Hi, my father and uncle (fathers brother) are joint owners of a residential plot measuring around 300 Sq Yards in Ambala City, Haryana. The plot was purchased way back in year 2001. Since the plot was vacant at that time. My father and uncle mutually agreed verbally that uncle can take the front portion of the plot to construct and to reside therein and my father will take the backside portion of the plot. This all happened in good faith.. My father was in loss as he agreed to take the back portion. However it was decided that my uncle will give a passage of aprox 7 feet to my father from his front portion to reach out to the back side portion. After this he constructed his house in front. Its been around 10 years that he is staying there. Now when my father wants to sell his portion of plot, my uncle is creating problem that he will not allow to sell the passage of 7 feet. Now no one is buying back side plot with exclusive right to passage. Plz advice what to do.