In a large pot over medium heat, saute the chicken in the oil for 5 minutes. Add the garlic and cumin and mix well. Then add the stock, corn, onion, chilli powder, lemon juice and salsa. Reduce heat to low and simmer for about 20 to 30 minutes.
Break up some corn chips into individual bowls and pour soup over chips. Top with the cheese and a little sour cream.