Set the Instant Pot® on Sauté mode and allow to heat for about 1 minute and then press Cancel.
Pour in the oil and then the milk. (The warmth of the Instant Pot® will get the milk to the right temperature to quickly proof the yeast.) Stir in the sugar and then the yeast. The mixture should become frothy within a minute or so.
Gradually stir in the flour and salt with a wooden spoon. The mixture will become crumbly. Stir in the yogurt and egg—this should be enough moisture to make a soft dough. Use your hands to press it all together into a ball (the objective is to have a soft smooth dough).
Cover the Instant Pot®, and set it on the Yogurt setting for 60 minutes.
Open the Instant Pot® to see beautifully risen soft and fluffy dough. Remove the dough and place on a working surface. Mix in a little extra flour if you feel the dough is too sticky. Break the dough into 8 lemon-sized balls and roll each to an oval about 5-6 inches in length and about 1/8 inch in thickness (the naans should be rolled out fairly thin as this allows them to puff up while cooking; you can use extra flour for rolling, but shake off any excess flour after rolling).
Heat a cast iron griddle for at least 2 to 3 minutes (test with water to ensure heat). Place one dough oval in the griddle. After a couple of minutes, it should puff a little at spots. Quickly turn on the other side and sprinkle with a few nigella seeds. Press the seeds gently to set into the dough. Cook for a couple of more minutes—the bread should be puffy and well browned and lightly charred at spots. Repeat with remaining dough disks. If desired, drizzle with a little butter before serving.