What if he blames Mauli
1) for lying to him about her pregnancy..
she lied to him and that is why he went to Nandini, they got married, they had sex, Nandini became pregnant n died...so he will be like you lied to me about your pregnancy why? you shouldn't have done that...see what you did? because of you and your daughter my Nandini died..because of you and your daughter, my and Nandini's daughter lost her mother...its all because of you I hate you and this daughter of yours.
2) Seeing Mauli with Ishaan
and thinking that Mauli cheated him (yes, Mauli cheated him just because Nandini died) and had a child with Ishaan. basically he is jealous that Mauli is living a happy life with his daughter and Ishaan and he it's sulking here because his divine love his Nandini died...
Anything else you think can happen?