Season chicken thighs liberally with salt and pepper. On Sauté setting of Instant Pot, heat olive oil until shimmering and sauté pepper and onion until soft, about 3-4 minutes. Add garlic, sauté 1-2 more minutes. Add paprika, smoked paprika, and onion powder, mixing into vegetables. Add chicken thighs, skin side down, and let brown 3-4 minutes. Stir in diced tomatoes. Place lid on Instant Pot, turn on Manual setting for 20 minutes with vent on “Sealing” setting. Let the setting run its course, waiting for the pressure valve to descend before opening the Instant Pot lid. Remove lid and take out chicken thighs, put them on a plate, and cover with foil. Turn Instant Pot to Sauté setting, bring sauce to boil and let reduce for 8-10 minutes. Plate chicken thighs, pour sauce over them and serve, garnished with sour cream if desired.