It sounds like you've ripped the fiberglass off. From experience, while you can seal the foam and the edges of the torn glass, it will act like a "cup" catching water, edges of the boat, your shin and eventually lift off. Also from experience it will happen JUST after you have loaded your boat and are 1.5 hours from the nearest tubes of epoxy.
The nose doesn't need any real structural interigty for a small slice. I would just either get a small piece of fiberglass to lay over the entire slice, or you can use a small piece of fabric like an old dress shirt cut up or a sheet.
To prep the area for repair. Lightly sand with 220 and remove any loose foam or other debris.
Mix up some of the 5 minute epoxy, wet the cloth out and smooth it out over the slice, using a plastic putty knife or squeege. When that has cured, fair the edges the surface of the board. To be doubly sure you have everthing covered, you can do a second thin coat of epoxy and then sand it through 600 starting at 150.
Hope that helps.