Why is my boyfriend have a ringworm on his nose and on his arm?

Contamination: Ringworm is a common name for a fungus that grows on outside skin tissue. The spores of the fungus can be found in soil, on animals or on people. If the spores contaminate your hands, fingers or fingernails, you can insert the spore on any outer skin surface. Over days or weeks the spore can begin a colony of the fungus that will feed on dead surface skin and grow outward in a ring.