Owner not returning full security deposit

Hi guys, I have a lock-in period of 9 months on the lease agreement. Agreement says if I move before lock-in he can keep security deposit . Now, I want to move after 4 months. Owner agreed , but adding lot of nonsense repair charges before returning security deposit. If I argue a lot , he is showing the lease agreement . What can I do here ? Do I have to obey him ? Can I do anything