The ability of Chandra's Pyreling triggers just once per event for each opponent who is dealt noncombat damage by a source you control, regardless of how much damage that player is dealt. For example, if a sorcery you control deals 2 damage to each opponent in a four-player game, the ability will trigger three times.

Combat damage is the damage that's dealt automatically by attacking and blocking creatures. Any other damage is noncombat damage, even if it's dealt during a combat phase by an attacking or blocking creature.