Set your Instant Pot to 'Sauté' mode. Add a drizzle of olive oil and sauté the chopped onion and minced garlic until they become fragrant and translucent.
Add the bite-sized chicken pieces to the Instant Pot. Sauté until they are lightly browned on all sides.
Stir in the rice and canned diced tomatoes (with their juice) into the Instant Pot.
Season the mixture with dried oregano, red pepper flakes, salt, and pepper. Mix well to evenly distribute the flavors.
Add chicken broth and tomato sauce to the pot. Stir to combine all ingredients thoroughly.
Close the Instant Pot lid and set it to 'Manual' or 'Pressure Cook' mode for 8 minutes. Ensure the steam release valve is in the sealing position.
Once the cooking cycle is complete, allow for a natural pressure release for about 10 minutes. Then, manually release any remaining pressure by turning the steam release valve to 'Venting.'