Heat 1 tablespoon olive oil in a large skillet over medium heat until shimmering.
Add the cubed chicken and cook, stirring occasionally, until browned on all sides, about 5–7 minutes; transfer to a plate with a slotted spoon.
Add the diced onion, sliced celery, diced green pepper, and minced garlic to the skillet and cook until the vegetables begin to soften, about 5 minutes.
Return the browned chicken to the skillet and sprinkle with paprika, crushed red pepper flakes (if using), cayenne, and oregano; stir to coat.
Add the 28 ounces petite diced tomatoes and 2 bay leaves, stir to combine, and bring to a gentle simmer.
Simmer uncovered for 10–15 minutes until the sauce slightly thickens and chicken is cooked through; remove and discard bay leaves before serving.