Training with warriors in Ruin and beat Grushk or in repeatable mission "Hunting Contest", choose to root for him and meet him in contest, explain to him and say you're sorry, that's all as far as I know.
There's also when you meet him near the waterfalls, when he meditating join him but you need a skill to be high enough in order to complete the meditation and if he's relaxing go close to him.
