What happens when you put lava in a pool of liquid nitrogen?

Depending on the amount of liquid nitrogen and the size of the lava flow, the nitrogen will regain it gaseous form well before it contacts the surface of the lava. However, due to the energy cost of bringing the liquid nitrogen back to a gas, it will cool the air above the lava by a few degrees, until that air is reheated by the lava itself.

Explanation:

The liquid nitrogen has enough coldness to completely cool down lava, but also it has the exact same energy to make lava explode.