Usually when we think of the word 'knowledge,' we think of knowledge of an object in the world of name and form.
But self-knowledge isn't the knowledge of an object. The 'self' which we are is not available to be 'known' in that way.
Perhaps, rather than using the word knowledge, a better word to use might be recognition. One recognizes what one always has been, but which was previously over-looked or misconstrued. Whatever we may think we are, until we recognize that which we truly are, isn't what we really are.
For a long time, I searched for my self as an object. Expecting this 'self' thing to pop out as something new and entirely different, something that would match up to the superlative descriptions I had heard.
When the 'self' pops out, as it were, it isn't recognized to be something new or totally different. It's known, as in recognized, to be who one has been all along.
Prior to that recognition whatever we think about it will be a concept. After that recognition, it's just kind like, "Oh, that's what it is all about." It might even be, "What's the big deal?"
But then as one gets to know one's self, as it were, the appreciation of this self which everyone is, grows.
The fact of consciousness is recognized by consciousness, but not directly, it can't be an object of perception. It's more like the ignorance, ideas about identity, are eradicated, leaving only being. When psychological ideas of self are absent, there is peace.
We accumulate spiritual "knowledge" because we imagine it will set us free. Actually, it is the imaginary bars on our imaginary prison. When we cease to believe in the bars, we realize it was never real to begin with.