Is it true that swearing a false oath has no expiation other than seeking forgiveness?

It appears the questioner is afflicted with waswasah (obsessive whispering/doubts), and he must disregard it. Doubt regarding an oath is not to be given any consideration, for the default is that no oath was taken. As for the yameen ghamoos (a false oath taken intentionally to usurp a right), the view of the majority of scholars is that no expiation (kaffarah) is required for it; rather, sincere repentance (tawbah nasooh) is obligatory.