In the fight in the forest, Kylo Ren kept punching himself in his injured side, like he was trying to make it worse or hurt more. Why? Was he punishing himself for killing his father? Was he trying to strengthen the Dark Side through physical pain? Was he angry at himself for being injured? Was it his light side, trying to hamper his fight against Finn and Rey?

What was the reason he did that, and why is it he thinks that way? Does he hurt himself in other ways at other times?