What should you do? Nothing, you are not the parent, you just gave a gift that was deemed appropiateappropriate by the parents.
You wrote yoruselfyourself that you didn't have a Nintendo when you were little but all your friends had one. Now imagine him not being able to play "pokemon"Pokemon GO" while all his friends can play it. I think it is the responsibility of the parents to know when he had enough "Playtime" anndand restrict the usage of the device. But seriously, he is 8 years old, of course he wants to play and have fun.