Assuming that your character is not specifically built for it to matter, it does not matter whether you use the knife or your fists.
In Cypher System, weapons generally only exist as light/medium/heavy and melee/ranged, and within those categories all have the same properties. That means any one light melee weapon is the same 2 damage with an asset on attacks as any other.
There are a handful of situations where the type of weapon does matter, though I'm not going to comb through all of the Cypher System... systems looking for them. I can, however, give the example of Numenera's Glaive Type.
Glaives in Numenera choose a particular type of weapon to gain certain bonuses with as they tier up, beginning with a bonus to damage. In this case, the game gets a little more granular with what that type is, dividing weapons up into light/medium/heavy and bladed/bashing/ranged. So a Glaive could choose to specialize in "light bladed" weapons, getting a +1 to damage with them. In this case, there is an incentive to pick the dagger back up.