Set Instant Pot to 'Saute' mode and add olive oil. Once oil is hot, add beef in a single layer to the Instant Pot. You may have to do multiple batches. Brown the beef on all sides. The beef does not have to be cooked through at this stage. Once the beef is brown on all sides, remove it from the pot and set aside.
Add onions, mushrooms, and garlic to the pot and cook until tender. About 3-4 minutes.
Add Worcestershire sauce, thyme, and flour to the pot. Stir until combined. Add beef broth to the pot. Stir to combine and make sure that you scrape up any bits that have cooked on to the bottom of the pot.
Add the beef back into the pot and cover with the lid. Set the valve to 'Sealing' and cook on 'Manual' at high pressure for 10 minutes.
While the beef is cooking, prepare the egg noodles according to package directions.
Once the timer goes off, let the pressure naturally release for 10 minutes. Then do a quick release by moving the valve to 'Venting'. (If the sauce isn't thick enough, you can make a cornstarch slurry by mixing water and cornstarch in a small bowl and then pour into the pot. Cook on 'Saute' mode until the sauce thickens to the desired consistency.)
Add sour cream to the pot and stir until combined. Stir in egg noodles and serve.