You should try to glue the crack in any way.
Even if you don't feel the crack while honing on the surface, if the crack will remain open, the water that penetrates in will most probably led to an enlargement of the crack. The crack from the side seems to be too wide for "normal" CA glue that can brige the gap, so I think hot glue will due better in this case.
Heat up the stone to approx. 80°C (slow heating i.e. in a backing oven) and then use a hot glue stick that you bring in contact with the coticule along the crack so that the glue melts and can penetrate into the crack. That seals the crack and prevents from an enlargement.
If you can feel the crack seriously while honing and the blades catches the crack it is more complicated to repair. You may have to enlarge the crack on the surface to a v-shape and then fill it with clue.
There is a very good guidance for repairing cracks in coticules (and also other hones) that you find here:
http://www.coticule.be/faq-reader/it...-coticule.html