All characters are self-insert characters. They are you a little to the left, or a particular piece of you dialed up to 11, or the you that you would have been if the path of your life had angled just slightly differently, or you if you never learned this one important thing.
Every character is part of you, but more than that every character starts with a piece of you, big or small, it’s you in one way or another at the beginning. There’s nothing wrong with that. In fact it’s essential. That seed of you, that lives in them, it’s what gives them life, breath and blood and bone. And then you tend it, growing it, shaping them along paths you could never have walked nor imagined for yourself. Until they become someone else entirely. A wholly fictional character. But also you, a little bit, somewhere in there in the heart of themselves.
Every character is a self-insert character. It’s only a matter of degrees how much of yourself there is in them when you finally put them out into the world. Stop worrying so much about self-inserts. Worry more about putting that little you into a story that will shape them into a big, beautiful character.