I would'nt get too nervous if it goes up a little.
Any inverts in the tank? If so, be sure to not let it get too high. Sombody has a quote that goes something like "a large water change will solve a multitude of sins". He/she is right with that. I forgot who says that though. Just keep an eye on it and you shoud be fine. Ohh ands hope you don't have a mantis shrimp in there...