Heat the olive oil in a large skillet over medium heat. Add the diced onion and bell pepper, sautéing until softened, about 3-4 minutes.
Add the minced garlic, and sauté for an additional 1 minute until fragrant.
Increase the heat to medium-high and add the ground chicken to the skillet. Cook, breaking it apart with a spatula, until fully cooked, about 5-7 minutes.
Stir in the diced tomatoes, Cajun seasoning, Worcestershire sauce, and season with salt and pepper. Mix everything thoroughly.
Lower the heat and let the mixture simmer for about 5-10 minutes, allowing the flavors to meld together.
Toast the burger buns if desired, then spoon the Cajun chicken mixture generously onto the bottom half of each bun.
Top with optional lettuce, pickles, and cheese, if using. Place the top half of the bun on and serve immediately.