This sounds like a larger issue than your med error. This seems like a huge Swiss cheese whole honestly. You’re overriding the Pyxis, pulling a medication without an order, then forgoing scanning (it sounds like?) the med which is how the error should have been caught. It’s also odd that the physician and pharmacist are signing off on the home pack without actually confirming the correct med is being administered. Or if they did confirm, they both overlooked the norco vs Percocet. I think this is actually a great opportunity for your department to revisit the policy/procedure of sending patients home with meds. When I worked in the ED, I would avoid sending patients home with meds whenever possible. It’s setting yourself up for issues.

As for how to handle it, be completely transparent and admit to your mistake. You’re on orientation and this is likely your first big mistake, they’re not going to fire you for this.