Leave it alone. Once fermentation has started you don't want to introduce any more oxygen. And you know that it has started fermenting, I gather. Moreover, dry yeast doesn't really require aeration, it has been grown in such a way that it brings with it everything it needs. The appearance of the kräusen is influenced by a lot more than just the vigor of the fermentation. At this point, follow the mantra: RDWHAHB (relax, don't worry, have a homebrew.)