Season chicken with salt and pepper on both sides. Heat the oil in a skillet over medium heat and cook chicken breasts 3-4 minutes on each side until cooked through.
Remove from skillet and set aside until cool enough to handle. Shred the chicken by pulling it apart with your fingers into small pieces and place in a medium mixing bowl.
Taste the pinto beans and if no more salt is needed, drain and set aside. If the beans taste flat or muddy, pour into a saucepan with the juices and add a teaspoon of salt. Bring to a simmer. Taste and add more salt if needed.
Mix the salsa and barbecue sauce together in a small mixing bowl. Taste and add more of either, as desired. Add enough sauce to the shredded chicken to cover well. Be sure to reserve some of the sauce to drizzle over the nachos just before baking.
Arrange 4-5 large handfuls of chips on a rimmed baking sheet. Sprinkle a layer of cheese over the chips (parts of the chips should peak through) and follow with a layer of chicken and beans.
Garnish with jalapenos as desired, and drizzle remaining sauce over the top. Bake until cheese is melted and beginning to brown and the chips are crisp, 8-10 minutes (check at 5 minutes). Remove from oven and garnish with cilantro and sour cream. Serve hot.