<p>Injuries in fencing are relatively rare - I fenced from high school until my late 30s, and then went back for a bit after that, and never actually saw a hand injury. (Well…I once got stung by a bee on my off-hand while fencing, but that’s another story.)
I would let a young child try as many things as is reasonable and not worry about injury issues in terms of finger dexterity until a child was very serious.
That being said, we would have steered ours away from contact sports - the risk of head injuries is far too high. (But it was never an issue.)</p>