I don't know what sort of a hole is in your leather nor where it is but superglue works fantastically well on leather. If the hole is in a non-stressed or lightly stressed area, carefuly apply a light application to the edges and hold them together for a few seconds until it sets. If the damage is to a more stressed area - like the bit you sit on, it may be necessary to remove the cover and reinforce the repair with patch of leather on the inside. After removing the seat the covers come of fairly easily, a few springs and clips to remove. Afterwards apply a suitable coloured boot polish and the repair should be almost invisible. This method may not be suitable if the leather is badly torn however in which case you may need a professional repair.
How did you damage it? Did you sit in it with a scewdriver in your hip pocket? I've nearly done that a number of times.