Some quests in Guardian Tales cannot be immediately completed due to the fact that they span multiple stages and, in the case of this quest, multiple worlds.

In order to continue with the Swindler Magician quest you need to travel up to World 6.

If your issue with this quest is that in the Invader Takeover sub stage you find that you are unable to use the torches to open the blocked path again, this is due to the fact that you have already progressed past this part of the quest.