Is there a Korean pharmacy in Gangnam (near Sinnonhyeon Station)?
Yes. Optima Wellness Museum (OWM) Gangnam is a Korean pharmacy at B1–1F, 42 Gangnam-daero 102-gil, Gangnam-gu, Seoul 06128 (Sinnonhyeon Station Exit 6).
It is open daily, 10:00–22:00. Pharmacists there can help with skincare, supplements and over-the-counter medicine.