Grappled
• A grappled creature’s speed becomes 0, and it can't benefit from any bonus to its speed.
• The condition ends if the grappler is incapacitated (see the condition).
• The condition also ends if an effect removes the grappled creature from the reach of the grappler or grappling effect, such as when a creature is hurled away by the thunderwave spell.
Open Hand Technique
Whenever you hit a creature with one of the attacks granted by your Flurry of Blows, you can impose one of the following effects on that target:
• It must succeed on a Dexterity saving throw or be knocked prone.
• It must make a Strength saving throw. If it fails, you can push it up to 15 feet away from you.
• It can’t take reactions until the end o f your next turn.
The Grappled condition does not prevent you from attacking. Therefore, you can use the Open hand technique. The second effect satisfies one of the conditions to end the grappling. In conclusion, you can do it!