The knowledge you acquired informally can feel less legitimate despite being no less usable.

Knowledge picked up outside an institution can feel like it does not count. You learned it by doing, from a relative, from years of practice, and because nothing certifies it you may discount it in exactly the rooms where it would be useful. The usability is unaffected and the confidence is not.

When you know something, say it, and let the question of where it came from be secondary. If asked, in my experience is a perfectly good source. Much of what circulates as expertise is less tested than what you learned by having to make something work.