4.5. Punch Biopsy (Tissue Sample): Punch biopsies pose minimal risk, and volunteers are instructed as to the proper care of the biopsy site. Lidocaine may cause a tingling or burning sensation when injected into the skin. Potential problems localized to the biopsy site include bleeding or oozing, discomfort, or infection. The biopsy site will heal with a small, flat scar, which may be red for several months. The scar may also turn lighter or darker than the surrounding skin after some time.