The phrase comes from Brazilian internet humor and is linked to a Twitch moment shared under the name pipocwb. Tá sujinho seu nariz is a joking way to point out something white left on a person's nose, with the source tags pointing to powder and flour rather than a literal dirty nose. Clips like this spread because the accusation is instantly understood in Portuguese-speaking meme culture, and the three-second line can be dropped over almost any guilty-looking face without needing setup or explanation.