If you do not lost this pin, it is no problem to fix the blade. Put it back, and from opposite site, using very small hammer, by 2-3 knocks, on the surface of home iron, made it tight inside its place. Do not use a lot of efforts, because there is a big risk to ripped the very fragile blade, and make it completely unusable. If you lost the pin, try to find small screw of the same diameter, make the same operation to fix it instead of the pin. There is the main reason I've never suggested to touch the old aperture unit. Good luck! LZ