how many did you add?
i'd personally wait at least two weeks to a month to let them get settled, and make sure your tank can handle the load. very least would be maybe three or five days if you want to be safe.
the first thing i'd add is more flame tetras, then. tetras should be kept in groups of at least six, preferably something more like eight.
anyways, if your tank is definitely cycled, the filter should be able to handle that bioload. still test your water quality and be sure your tank is 0 on ammonia and nitrite before getting more fish.