Praise be to Allah.
There is nothing wrong with you teaching English, if your work meets Islamic guidelines and does not involve free mixing or wanton display.
There is also nothing wrong with you refraining from teaching; that does not come under the heading of concealing knowledge as mentioned in the report narrated by Abu Dawood (3658), at-Tirmidhi (2649) and Ibn Maajah (264) from Abu Hurayrah (may Allah be pleased with him) who said: The Messenger of Allah (blessings and peace of Allah be upon him) said: “Whoever is asked about knowledge and withholds it, Allah will bridle him with reins of fire on the Day of Resurrection.”
What is meant by that is the one who is asked about Islamic knowledge when the people have a need for it, or he has knowledge that no one else has; in that case he is obliged to disclose it and it is forbidden for him to conceal it.
It says in ‘Awn al-Ma‘bood (10/66):
“Whoever is asked about knowledge” refers to knowledge that the questioner needs to know, having to do with his religion.
“and withholds it” by not answering, or by withholding the book.
“Allah will bridle him” that is, Allah will put in his mouth a bridle
“with reins of fire” as recompense for him having bridled or restrained himself by keeping quiet. End quote.
Al-Qurtubi (may Allah have mercy on him) said in his commentary on the verse, “Indeed, those who conceal what We sent down of clear proofs and guidance after We made it clear for the people in the Scripture - those are cursed by Allah and cursed by those who curse” [al-Baqarah 2:159]:
It was said that what is meant is everyone who conceals the truth. It is general in meaning and applies to everyone who conceals knowledge of the religion of Allah that is needed to be disseminated. This is explained in the words of the Prophet (blessings and peace of Allah be upon him): “Whoever is asked about knowledge [that he knows] and withholds it, Allah will bridle him with reins of fire on the Day of Resurrection.” Narrated by Abu Hurayrah and ‘Amr ibn al-‘Aas; narrated by Ibn Maajah…
From this the scholars understood that it is obligatory to convey true knowledge, and to disclose knowledge in general, without charging a fee for it, because a person does not deserve payment for doing what he is obliged to do, just as he does not deserve payment for becoming Muslim. We have discussed this previously.
What the verse means is: if a scholar deliberately withholds knowledge, he is sinning.
If he does not withhold it that deliberately, he is not obliged to convey it if he knows that someone else also has the same knowledge.
As for the one who is asked, he is obliged to convey that knowledge, because of this verse and this hadith.
End quote from Tafseer al-Qurtubi (2/184).
It is possible to combine worldly work or teaching with the pursuit of Islamic knowledge, if you organise your time and strive hard.
Working could be a help in that it may enable you to afford to buy books or pay fees for courses in pursuit of Islamic knowledge.
If the administrative job will give you more time to seek Islamic knowledge, then it is better in that regard, but teaching has an extra advantage, which is that it is a means of connecting with the students and undertaking the mission of guiding them and calling them to Allah, may He be exalted, and benefitting the Muslims.
If you are able to work now in teaching English, at the same time you can join an Islamic college, so that you can get a bachelor’s in Islamic studies – either in sharee‘ah or usool ad-deen.
Then after you complete that, you can change your work to teaching Islamic knowledge, and perhaps there will be much good for you in that, and you will be able to meet your needs. Thus you can combine all your interests, and you can acquire Islamic knowledge and become a teacher thereof, which is a good profession; it is no secret that there is great reward and benefit in that.
So try hard to choose that which is appropriate for you and which you feel that you are able to do and have an inclination for, and which you think will bring you closer to Allah, may He be exalted, and will enable you to attain beneficial knowledge.
And Allah knows best.