Saute flour in oil for 8 minutes or until the flour browns. Remove from pan and reserve. Add onions, celery and bell pepper to the same pot. Saute for 5 minutes. Add cajun seasoning and saute for 5 more minutes. Add stock, worcestershire, tomatoes, beans and reserved roux. Bring to a simmer for 5 minutes. Add chicken and simmer for 10 minutes. Add hot sauce, serve over rice, topped with sour cream.