Hi
It's not worth the chance it may have a microscopic crack in it and it will fall just by pushing it back to the right size just buy a new one they are cheap to replace..
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Replacing it is the obvious safest choice, but if it were me, I'd fix it first. If it doesn't crack (and I don't think it will), it should be fine. A 1/2" diameter rod with a chamfer, or a 1/2" diameter tapered punch should work. An old 1/2" drill bit would work too. Don't use anything bigger than 1/2" in diameter.
Also, the retaining nut holds the collet in. Even if one of the tangs is cracked, it should not cause a problem during use since the nut retains it and jams it against the bit.
I think there's very little danger of breaking a tang since it doesn't move very far when compressed without a bit (and then bent back) and, if it is cracked, it will eventually fall apart, preventing a bit from being inserted.
You should pay special attention to it to make sure the bit is going in properly but once it's in, if everything looks fine, I think it shouldn't be a problem.
