Place the chicken breasts in the Instant Pot. Add the salsa, chicken stock, chili powder, taco seasoning, ground cumin, lime juice, and lime zest. Season with kosher salt and freshly ground black pepper to taste, and toss to coat.
Close and lock the lid, set the valve to Sealed, and cook on high pressure for 10 minutes.
When the cook time is done, perform a quick release according to the manufacturer's instructions. Open the lid and transfer the chicken to a medium bowl.
Shred the chicken with two forks until it is in bite-sized pieces and season with salt and pepper to taste. Reserve any remaining cooking liquid if desired.
Preheat the oven to 400°F (200°C) and lightly oil a rimmed baking sheet.
Arrange the tortilla chips in a single layer on the prepared baking sheet. Top with about 2 cups of the shredded chicken (reserve the rest for another use), spoon pico de gallo over the chips, then sprinkle evenly with shredded cheddar cheese.
Bake in the preheated oven until the cheese is melted and the nachos are heated through, about 10–12 minutes.
Remove the nachos from the oven and immediately top with guacamole, sour cream, sliced jalapeños, and chopped cilantro. Serve right away.