Curious wants to understand. Nosy wants something to repeat. Be the first one.

Both look identical from outside and they differ entirely in where the information is headed. One is trying to make sense of a person, the other is gathering material. People feel the difference almost immediately even when the words are the same, which is why some get told things and others stop being told anything. What you do next is the tell.

Before you ask something personal, check where you are planning to put the answer. If part of you is already imagining telling somebody, that is worth noticing. Ask anyway if you can hold it, and then actually hold it.