To reset, i.e. dissociate a default construction set from a story:

• mouse-click on the set (it'll be highlighted in yellow)
• mouse-click "Remove object"

The "removed" default construction set will remain available e.g. for other stories or spaces in the model.

PS: You may want to edit your initial question. "I applied a construction set to a particular construction set"; I suspect you meant "I applied a construction set to a particular story".