Definitely get a hydrometer or two for next time as it can cause damage in different ways if too low or two high.
But for the present, hatching will create its own humidity from the eggs and chicks drying.
I would probably pull the chick into a nice warm brooder as it will be weaker from...
I do believe flour will also work. I had read somewhere you can dip his navel in sugar to be absorbed into his bloodstream (for energy) and act as an antibacterial.
What's the humidity like in the incubator?
I pulled the chick I had in the incubator when it had an incompletely closed...