Swirling Blades

Two daggers appear and begin swirling you. 

You may make any number of them immediately fly to a target within range as either part of the action used to summon them, or as a bonus action on following turns.

As a reaction to being attacked, one may fling any number of the daggers at an attacker, immediately before they attack. Additionally, if concentration is broken by an attacker, these blades automatically fly to them. 

A dagger deals 1d4 + 1 piercing damage to its target. 

If all the daggers are used, or concentration breaks, these daggers disappear.

At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the spell creates one more dagger for each slot level above 1st.