In reply to SteveJC94:
I get these seriously bad. Usually every winter, but now I'm climbing outside regularly, they've come back.
I find glueing them doesn't really work, as superglue is incredibly brittle, so just breaks with movement and then causes the split to worsen.
The fastest way I've found to heal them is by taping them up with a plaster. Apply some wax of some sort (such as your rhino skin), and also rub the wax into the pad of the plaster. Then cut the plaster up to the pad like in the photo, and wrap it fairly tight, applying pressure in the direction that'll close the cut. It stings for 5-10 minutes but then you don't notice it.
I'd personally stop filing the skin and keep up with the moisturiser once they've healed to try and stop more appearing.
They're so damn debilitating, and if I try to describe the pain to those that haven't had them before they think I'm over-exaggerating!