wouldn't worry about it, I would say it'll be all over the place for a few weeks at least. Just don't add anything for a while.
This is one of the reasons why I can't understand people that add stock after 1 or 2 weeks (not saying you have), the nitrogen cycle may have finished but the pH, alkalinity and all the other parameters will be nowhere near stable. People should leave at least 2 months before adding stock even if the ammonia/nitrite/nitrate is ok.