It does not look like a fungus or bacteria infection. Looks like physical damage, something bumped or knocked it. Like a bruise. Just keep a eye on it. So it does not become an enterance/vector for bacteria or fungus to get into the leaf and wreck havic. As stated above by Orchid Whisperer, jkofferdahl, and estacion seca
Before posting here I have visited several websites with photos of diseased plants and the most similar spots are those of Erwinia.
Today, the spot seems to be unchanged in side which is a good sign because Erwinia spots grow noticeably from day to day, and sometimes kill a plant in few days.
If you see the photos, the affected area was in touch by the edge of the leave beneath. I've moved the leaf to the side but originally the edge was contacting that area.