aww ok so Nikhil went for his bday celebration to his ancestral village.there while trying to save lajjo's life in river ,he and lajjo had to spend night away from village and when they came back next day villagers were mad. Thus his grandfather suggested that Nikhil should marry lajo(this is brief but it was very interesting time in show) obviously his family in Delhi hated it Also Nikhil carries guilt about his older brothers death in childhood in a roof top accident, Nikhil couldn't hold on to his brother and he slipped. So he somehow connects it to lajjo and wants to save her from villagers.
Now he brought her to city but still loves ishana .every one in family were shocked but most have accepted lajjo as she is really good girl, she lives in Nikhil's guest house. Nikhil tried breaking marriage once but couldn't due to lajjo's very nice parents so he told Lajjo I wil protect you but never love you.
Now ishana played many games and started instigating Nikhil against Lajjo.
In general Nikhil has always cared for lajjo as a friend and supported her many times that made Lajo fall in love with him .
Family is kinda not sure how to react to ishaana while his mom and nani openly support ishana.but ishaana's mom hates it .so in nut shell now Lajo left Nikhil for his own sake
I hope its enough but try watching epsiodes at desi tashan or some other site they r really good.