Whenever Kolaghan Aspirant becomes blocked by a creature, Kolaghan Aspirant deals 1 damage to that creature.
If Kolaghan Aspirant becomes blocked by multiple creatures, its ability will trigger once for each of them.
The damage Kolaghan Aspirant deals because of its triggered ability isn’t combat damage. If that damage causes each creature blocking it to leave combat, Kolaghan Aspirant will remain blocked. It won’t be dealt combat damage in this case.