You've learnt the first ability in the Way of the Closed Fist, The Focused Strike. This ability allows you to focus your Ki into into your fists for a single devistating punch. 

• On your turn, when you score a critical hit with an Unarmed Strike or reduce a creature to 0 hit points with one, you can make a Flurry of Blows attack as a bonus action without spending a Ki point.
• Before you make a melee attack with a Unarmed Strike as an action, you can choose to take a -5 penalty to the attack roll. If the attack hits, you add +10 to the attack's damage.