When I worked with an Infectious Disease (ID) doc, he had a case where a young woman mid-20's or so, had a bump on one of her fingers. It was diagnosed as a mycobacterium species found in water. She related that she had been fishing about 6 months previous. The doc felt that was where this was contracted, perhaps by a small open area in the skin. She took meds and it resolved without issue. Various mycobacteriae exist commonly in our environment. They live in the earth and water. No expence with nocardia.