Combine the Arborio rice, water, and sea salt in the Instant Pot inner pot.
Secure the lid and set the steam release valve to the sealing position.
Select the Manual or Pressure Cook function on high pressure for 10 minutes.
Allow the pressure to release naturally for 10 minutes before manually venting any remaining steam.
In a separate medium bowl, whisk together the Greek yogurt, egg, maple syrup, vanilla extract, and ground cardamom until completely smooth.
Open the Instant Pot lid and select the Sauté function on the lowest heat setting.
Slowly pour the yogurt and egg mixture into the hot rice while stirring constantly to prevent the egg from scrambling.
Continue to stir for 2 to 3 minutes until the pudding thickens and reaches a velvety consistency.
Turn off the Instant Pot and fold in half of the pistachios.
Serve the rice pudding warm or chilled, garnished with the remaining crushed pistachios.