hmmmm, why did you need to remove it?
as you have found out, they are not easy to remove, which is how it is supposed to be - the star arms dig into the metal as you try to pull it out.
if the other end is open, you normally bash tehm out but that doesn't appear to be so in your case.
therefore you need to break it for it to come out - drilling it one way.
looks like yours is on tis side, you can try hooking a peice of wire and pulling it although I suspect that may not be strong enough.
else leave it in and fit another star nut.
(I don't think I could live with it like that as the redundant nut would grate on me but others I am sure would).