Is it permissible to break a promise and covenant with Allah to abandon social media platforms, such as Facebook, in order to return to them for the purpose of work and دعوت إلى الله (inviting to Allah), while fearing to violate the promise?

If what was issued from you was merely a promise: "I promise Allah to do such and such," then nothing is binding upon you, because it is neither an oath nor a vow. However, it is desirable to fulfill it, especially since it is a promise made with Allah. But if it was a covenant: "I covenant with Allah to do such and such," then there is a difference of opinion among scholars regarding it. And if your statement "I swore inwardly" was merely a self-dialogue, then nothing is binding upon you, due to the Prophet's (peace and blessings of Allah be upon him) saying: "Indeed, Allah عز وجل has overlooked for my Ummah what they whisper to themselves, as long as they do not act upon it or speak of it."