When Starkiller base exploded, Ren appeared to be on it still, either way, he wouldn't have had enough time to get off of it before it exploded, so how did he survive? And if so, how without serious injury?
In the final moments before the Starkiller Base explodes, Supreme Leader Snoke, in all of his hologram glory, instructs General Hux to evacuate the planet with Kylo Ren. It is safe to assume that Kylo and Hux managed to evacuate the planet using one of the First Order's fancy spaceships, and live to fight another day against the Rebel Alliance.
However, I wonder How BIG and explosion a planet-sized superweapon would create...