You probably fixed it already, but heres what I did to preserve the OEM part instead of replacing it with cheap made in china part..
Buy a small needle point curved tweezer, they are anywhere between 5-8 bucks, or like me to borrow it from your girl friend or wife.
Pick the small pin up with the tweezer and just push it in a little with your thumb so it doesn’t drop, and pinch close to the tip to add security.
Make sure to bend the hinge so you have a little more room to work with.
Lightly insert the pin carefully into the hole, DONT push yet.
Make sure that the pin is in the hole already, then push it in with small size flat head screw driver.
This is exactly what I did.
and sold this &&^&@@ up quality headphone afterwards for 40 bucks, minus the broken headband for 15 dollars… 25 bucks..
Good luck, and I hope people sees this if they want to fix it and use it themselves.