What is the ruling on my ritual purity (taharah) if I have not experienced menstrual bleeding, but I saw a small amount of brownish discharge once, and then I checked and the cotton swab was clean (white), and must I wait?

The brownish discharge before blood is not considered menstruation by some scholars, and Ibn Uthaymeen preferred this view. If the blood that follows reaches a total duration of one day and one night, it is considered menstruation, and ghusl (ritual bath) becomes obligatory after its cessation. Otherwise, it is not considered menstruation by the majority of scholars. Performing ghusl to avoid scholarly difference is a good thing.