Hi Hon, I was in the same predicament just yesterday. Take a look at my chart & u'll find my temp dip was far more drastic ...
But that said, the ladies here on BnB told me to hang in there & that 1 odd temp is no reason to panic. It could be a fluke reading due to various factors such as earlier temping time, cold conditions in the room, sleeping with your mouth open etc. Did any of these factors hit you? Or it could have been due to a sudden estrogen surge.
As mentioned by Heidi, 1 reading doesn't mean much as FF looks for a pattern. So stay positive that your temps returned to high levels tomorrow.