Well, for that age group I would suggest not making a big deal out of it.. .I mean, acting like it's not a big deal. I can hear them ask, how did you get cut? You know?

Just say, nochalantly, Oh sometimes things happen don't they? Have you ever had a boo boo? (or whatever word they might use) ... odds are they will spend the rest of the time telling you about all the mishaps they've had... it sounds like they could use someone to listen and care about them!

Or you could say, oh let's not talk about me, tell me about you and when you got hurt (or something...)

It you don't make a secret big deal out of it, they probably won't bother about it again.