You can find these items in the Face Accessories category in Create-a-Sim (CAS). They are often found under earrings or nose rings, depending on the specific file.
Magic-bot often recommends using their custom jaw and cheek sliders to ensure the piercings align correctly with your Sim's face, especially if you use extreme facial proportions. CONE PIERCINGS #1-33 at Magic-bot
To use them, download the .package files and place them into your Documents/Electronic Arts/The Sims 4/Mods folder. Ensure Custom Content and Mods are enabled in your game settings. You can find these items in the Face