Bindu is the Key of CN relation...

And also when Chandra hide Nandini face from the portrait with Dhuru he remove Chandra hand..

So i think whenever Chandra try to remove Nandini from his heart and Life Bindu always bring her back anyhow... with her memory or belonging or even with herself

Due to Bindu I think in future Nandini come back...

But today we can see unspoken connection between Bindu and Nandini..