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Looks like the nostril is clogged with dirt, food or something.
Try working it loose. Apply 1 Drop of peroxide to the material that inside the beak. Let the Peroxide sit for a few minutes, then work on the material. You can use something like an orange stick or plastic toothpick. Only apply 1 drop of peroxide at a time, then work on it. You may need to do this over a period of days.
If you have an existing flock, then I'd keep the newbie separated out until you are able to observe them for a while.