Unless there's a reason to remove them, like they need replacing for some reason, it might be better to just leave them in place.
Just treat them as part of the cylinder and quit while you're ahead.
I have a Remington, gotten used, with the nipples so rusted in place it's just about guaranteed they will break off with any attempt to remove them.
And so far, nothing tried has persuaded them to loosen.
So, I just leave them there and avoid risking a real headache.
It shoots just fine that way.
Just a thought.
Like the old adage, "When in doubt, don't."