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violalore
Depends, if you decide it's nerve or bone damage or both. Bone damage in my books is sure death for a skydancer, while nerve damage needs mandatory assistance of other dragons to help. However, considering it's a plague dragon, whatever type of physical damage it takes could be healed by it's own power infused by the Plaguemother, but if it need others to help is an horrible shame not worth to be living (in my plague lore).
(My own personal lore here, as both veterinary medicine student an plagueling.)
I see dragons more related to birds (reptilia-birds), and specially skydancers and coatls. Those animals have light bones to ease flight, but also an improved respiratory system that doesn't need a diaphragmatic muscle and could even survive with less developed lungs... but no without its wing's and leg's bones.
Bones in birds (and dragons in my lore) are associated with air sacks that compose the 80~90% of the respiratory system, sending oxygen almost directly to tissues and organs without need of too much blood transport. When birds and some reptile come broken to my clinic it's almost a sure death, because hematomas and vessel damage usually flood the air sacks when enter the bones, or the sack itself collapses due to severe and exposed damage of the bones. So the most common cause of death in traumatic damage is not blood loss, nerve damage or those typical of mammals, but asphyxia.
Well. Now about plague magic healing.
In my lore plague dragons can use their magic power to have some telekinetic and necromantic control over bones, blood, catalytic proteins (those who turn damaged tissue into ...even more damaged tissue), and even corpses. 'Cause of that, Plague magic gift medics with awesome abilities to control traumatic damage, both enhancing and inhibiting it.
But plague magic also infects with the Wyrmwound Virus the body of everything it touches, inhibiting most of mutation and mitosis control of the non adapted organisms and any other attempts to infuse healing magic do damage instead, so can only be used to heal plague dragons or dragons who have been following the path of the Plaguebringer in the Scarred Wastelands their entire lives.
As your skydancer is a Plague Rep, it could "heal" itself, at the cost of large amounts of energy (and thus be well fed) to control the expansion of damage and repair it. If the dragon manages to have a moment of rest, the healing process could be really fast.
In the scarred wastelands, whatever is too weak to stay well fed, will die without having energy to fight, fly or heal using the plague magic. The gift of life is given to everyone, but just the strongest will remain. However, there's a large misconception about plague dragons never aiding others: The Mirror dragon, whose social structure and beliefs are the basis of all plaguelings, DO help other dragons, specially those who they consider important and respectable enough. They are like wolf packs, and they'll help their most respectable comrades when misfortune tries to destroy them, only leaving them when are not worthy enough, or the aided claims it's an honor to be left alone in a fight for survival.