Place the potato in a small pot of salted water, bring to a boil, and cook until tender, about 10-12 minutes.
Drain the potato and let it cool slightly before dicing it into bite-sized cubes.
In a medium bowl, whisk together the Greek yogurt, Dijon mustard, lemon juice, chopped dill, and half of the salt and pepper.
Fold the diced potato, chopped celery, and minced red onion into the yogurt mixture until well coated.
Pat the salmon fillet dry with a paper towel and season both sides with the remaining salt and pepper.
Heat the olive oil in a non-stick skillet over medium-high heat.
Place the salmon in the pan skin-side down and sear for 4-5 minutes until the skin is crispy and golden.
Flip the salmon and cook for another 2-3 minutes until the fish is opaque and flakes easily with a fork.
Serve the warm salmon fillet next to the chilled, creamy potato salad.