What is this hard lump on your nostril that hurts when touched and swells up?

It could be a boil or a pimple. Boils are caused by a bacterial infection that starts in a hair follicle. They typically occur on the face, neck, or back, and can be quite painful. Pimples are caused by a buildup of oil, dirt, and dead skin cells in a pore. They are usually smaller than boils and not as painful. If the lump is large or causing you a lot of pain, you should see a doctor.