Exactly. It can mean several things, not necessarily "pricked". But the PGP have a tendency to choose the most negative translations. But considering that RS had already written that he "brushed her hand" with the knife, the odds are he was meaning he'd touched her hand with the knife, not pricked it.
Regardless, there is no way that knife was used to kill Meredith as her blood was definitely not on it and any bleach cleaning would have destroyed her DNA anyway.
I continue to agree with what you've written, but I've done a little linguistic detective work using Google Translate to investigate the mystery. Contrary to part of my earlier thought that words previous to the key phrase (with
punta) influenced the translation, it seems that words following it make the difference. Here's my small experiment in computer translation - first, I translated up to and including the key phrase, then with the full text of the two sentences.
1.
l fatto che c’è del Dna di Meredith sul coltello da cucina
è perché una volta mentre cucinavamo insieme,
io, spostandomi in casa maneggiando il coltello,
l’ho punta sulla mano,
The fact that there's Meredith's DNA on the kitchen knife
is because once, while we were cooking together,
I, moving around the house handling the knife,
pointed it on my hand,
2.
l fatto che c’è del Dna di Meredith sul coltello da cucina
è perché una volta mentre cucinavamo insieme,
io, spostandomi in casa maneggiando il coltello,
l’ho punta sulla mano,
e subito dopo le ho chiesto scusa ma lei non si era fatta niente.
Quindi l’unica vera spiegazione a quel coltello da cucina è questa.
The fact that there's Meredith's DNA on the kitchen knife
is because once, while we were cooking together,
I, moving around the house handling the knife,
stung her hand,
and immediately afterward I apologized, but she hadn't hurt herself.
So the only real explanation for that kitchen knife is this.
Conclusion: It's the context
after the key phrase that determines
whose hand is affected. Stung is similar to pierced or pricked in meaning.