Inductor suddently conected to current source
In the instant after the switch is opened, L1 acts as a 1 A current source.

At the same time, L2 acts as a 0 A current source. 

As in other cases where you put ideal current sources in conflict, what that means is that you have an incomplete model. 

You will need to consider parasitics in the circuit, particularly the inter-winding capacitance of the two inductors, to make a reasonable model to predict the circuit behavior.