In a bowl or zip-top bag, combine lime juice, 2 tablespoons olive oil, garlic, cumin, paprika, oregano, salt, and pepper. Add chicken thighs and toss to coat. Let marinate at room temperature for 15 minutes while you prepare the sauce and toppings. Do not marinate longer or the lime will start to 'cook' the chicken.

In a blender or small food processor, combine avocado, sour cream, lime juice, jalapeño (if using), cilantro, and salt. Blend until completely smooth, adding water a tablespoon at a time until it reaches a drizzly, creamy consistency. Taste and adjust salt or lime. Cover and refrigerate until ready to use.

Heat a large cast-iron skillet or heavy pan over medium-high heat until very hot. Add remaining 1 tablespoon olive oil. Lift chicken from marinade, letting excess drip off (discard used marinade). Place chicken in the skillet in a single layer, smooth side down. Cook without moving for 5–6 minutes until deeply golden and charred in spots. Flip and cook another 5–6 minutes, or until internal temperature reaches 165°F (74°C). Transfer to a cutting board and let rest 5 minutes.

Slice the rested chicken against the grain into thin strips. Warm corn tortillas in a dry skillet or directly over a gas flame until pliable and lightly toasted. To assemble, drizzle a spoonful of avocado sauce on each tortilla, pile on sliced chicken, then top with fresh pico de gallo (tomato, onion, cilantro) and extra squeeze of lime.