Honestly I'm surprised there have been so many threads about this. One or two threads was one thing, now it's like a slight common thing and it just leaves me baffled...
Do people not even read through the entire warning you get before you go to actually nuke the planet? The warning's right there the first time you click telling you, in full detail, that consequences would happen with Myrellion as a whole if you do it, it WARNS you right there about the planet possibly getting glassed if you activate that nuke, second time on the same button is basically you confirming and thus activates the nuke despite the clear cut warning, so you have an extra click to think about what you're doing, and if you do that extra click you should be well aware of what you're locking yourself out of once you do.
Quite a way to punish those that don't read and/or think about what they're doing. Which is ironic for a fricking TEXT game imo. Unless one has a goal to blow up all the planets that allow said blowing up, or is still encountering that old weird bug for... god knows what reason exactly, I almost feel like the whole Myrellion nuke thing shouldn't be this frequent of an issue at this point. >.<
I probably sound a little rude, but if one doesn't take the time to sometimes read thoroughly in this game rather than bum-rushing through, consequences could and possibly will happen. And Myrellion's nuke was telling you clear as day as to what would happen, it's basically telling you "Don't do it, bad things will happen to the planet if you do." in a way. I suggest saving BEFORE you do a major dungeon when you take risks like that, or better yet and what's probably more recommended, save the same character in a completely separate save file before you even do said dungeon period, that way your main file won't be screwed over as a whole while your secondary file will be after you go "Okay so this does this, and this does that, and don't do this because it'll fuck me up and so will that and etc. etc.". Trust me, it saves you a lot of hassle.
As of now, you're probably out of luck unless you know how to save edit. I don't know how to do any of that and don't save edit in general, so you might need to restart and work your way over there again. The game's pretty easy to get through as a whole. Lesson learnt not to do it again at least.