What tool do I need to unscrew the orange tip of my JG m4a1?

Ok guys I'm trying to put a silencer on my airsoft JG m4a1 and I already know how to take the orange tip off put there is a little screw thing holding it in place. It's not actually a screw but it's a thing that has a little thing sticking up in the middle of where the screw part would be. I'm wondering if anyone knows the tool that I need to take it off