Talking to son about self harm scars

[TheGnusShoes]

I would appreciate some advice if anyone has any. I have a few visible scars on my arm from past self harm (years ago) and I think my DS (just turned 5) has begun to notice them and I'm anticipating questions. The problem is I don't know what to say, I don't want to close the conversation off forever as I'd like to be able to discuss this type of thing as he grows up but I think he's too young to understand now.
So my question is how would you answer questions in an age appropriate way that doesn't make him feel that he can't broach the subject in future.
Thanks for anyone reading!

Cinderella I also think that's very poetic, and probably as close to the truth as you can get with a young child. I would be interested to know though... what do/would you say if they asked you whether monsters are real?

I made up a vague accident story then told them when they were mid-teens. I'm usually a parent who tells the truth but it's too complicated to explain and for them to understand. Once they'd had a year or two in secondary, they were more aware of mental health and self harming so could ask questions etc

@JesusInTheCabbageVan she did go through a stage of being afraid of monsters last year, I didn't want to just tell her that monsters weren't real because to her they were real and she was scared so instead we had monster spray (water in a spray bottle) and I told her I knew how to fight monsters anyway. She stopped mentioning it a few nights after we started the monster spray.