Heat olive oil in a large pot over medium heat.
Add diced onion and sauté until translucent, about 3-4 minutes.
Stir in minced garlic and cook for another 1 minute until fragrant.
Add diced chicken breasts and cook until no longer pink, about 5-6 minutes.
Pour in chicken broth, great Northern beans, and mild green chiles with their juices.
Add corn kernels, chili powder, ground cumin, dried oregano, salt, and black pepper.
Stir well to combine and bring to a simmer.
Reduce heat and cook for 10 minutes, allowing flavors to blend.
Remove from heat and gently stir in sour cream until creamy and well incorporated.
Serve hot with your favorite toppings or sides.