How should I comfort my best guy friend?

My BGF transfered this year. He seemed cool about it til I started school without it. But, now he's saying sorry for everything and always wants to hang out. Yesterday we hung out for four hours just talking. Today we hung out for seven hours! Riding bikes, talking, and working on our clubhouse. He's texting me alot now. Also, today he even met me at the school and we walked home together. He seems very sad. He even addmited it. I really miss him too. But what should I do to comfort him?