While the chicken marinates, prepare the ranch dressing by whisking together the ranch, sour cream, hot sauce, lime juice, and cilantro in a bowl. Chill until ready to use. Then prepare the pico de gallo by finely dicing the tomatoes and red onion and tossing with lime juice, salt, black pepper, and minced cilantro and jalapeno. Cover and set aside.
Remove the chicken from the marinade and pat dry. Use a meat mallet to pound chicken to an even thickness. Season with salt, pepper, cumin, and oregano. Preheat the oven to 375°F. Heat an oven safe pan over high heat and drizzle with olive oil. Add the chicken to the pan and cook for about 5 minutes per side.
Once leftover fiesta lime chicken has cooled, you can transfer them into an airtight container. Afterward, store the leftovers in the refrigerator to eat within 3 to 4 days.