Here, something blocks a gland around a hair or irritates the opening (follicle) that holds it, often on your face, ear, head, trunk, or groin. That causes a bump to grow slowly under the skin. It’s usually soft enough to move when you touch it. Usually, it doesn’t hurt, but you might notice a bad smell. Smaller ones usually go away on their own, but your doctor may need to drain or remove larger, swollen, or painful cysts.