Season the chicken thighs generously with salt and pepper.
Add the vegetable oil to a large heavy-bottomed stock pot or skillet set over medium-high heat. Once the oil is hot, brown the chicken thighs on both sides, working in batches and adding more oil as needed. Transfer the browned chicken thighs to a plate and leave all drippings in the pot.
Reduce the heat to medium-low then add the onions, garlic, drained tomatoes and bell peppers. Cook, stirring, until the vegetables are softened, 3 to 5 minutes, scraping up any brown bits from the bottom of the pot. Stir in the paprika and cook for 1 minute.
Stir in the chicken broth then return the chicken to the pot. Bring the chicken to a boil then reduce it to a simmer and cook until the chicken is cooked through, about 15 minutes.
Remove the chicken to a plate. Increase the heat to medium-high and boil until the liquid has reduced by 1/3. (NOTE: YOU CAN STIR IN SOUR CREAM AT THIS POINT AND SERVE, BUT I LIKE TO BLEND FOR A SMOOTH SAUCE.)
Carefully transfer the hot liquid to a blender then add the sour cream and blend until smooth. Taste and season with salt then pour the sauce back into the pot. Return the chicken and serve atop nokedli (spaetzle).