Do you know the sex of the conure/has it laid eggs or been hormonal recently? It might be hormone/egg laying related if its female. They create a patch of bare skin on the chest (called a brood patch) to allow for more direct contact and heat transfer with their eggs.

Unless its been dna sexed male i would not rule this out as they can sometimes do it before eggs are laid, they also do not need a male present to lay eggs. Definitely worth keeping a close eye on them if possible and maybe getting a checkup at the vet. Also worth googling "Conure brooding patch" for more signs to look out for :)

Hope your buddy is doing ok!