Pound the chicken breasts to even thickness, then rub them with olive oil, chili powder, cumin, salt, and pepper.
Grill the chicken over medium heat for about 5 minutes per side or until fully cooked. Let rest, then slice thin.
In a small bowl, mix sour cream, lime juice, and chipotle hot sauce (if using).
Warm the tortillas in a dry skillet or microwave for 10 seconds to soften.
To assemble: lay out a tortilla, spread a spoonful of the sauce, add sliced chicken, cheese, lettuce, tomato, onion, corn, and beans.
Roll up tightly like a burrito. Slice in half and serve immediately—or wrap in foil for on-the-go lunches.