This is a question that has been asked and answered many times.
It is narrated on the authority of Abu Huraira that the Messenger of Allah (ﷺ) said:
"Men will continue to question one another till this is propounded: Allah created all things but who created Allah? He who found himself confronted with such a situation should say: I affirm my faith in Allah." (Sahih Muslim 134)
And he reported: The Messenger of Allah (ﷺ) said:
"Satan will come to one of you and he will say: Who created this and that? until he says to him: Who created your Lord? When it comes to this, let him seek refuge in Allah (from the Shaytaan) and stop such thoughts. (Sahih Bukhari 3102)
Concerning this narration, Shaykh Ibn Taymiyya (may Allah have mercy on him) writes in his book Dar at Ta'arud al-Aql wan-Naql:
"It is known by necessity and human nature, for all who have sound nature among the children of Adam, that the question is invalid. It is not possible for the Creator of the creation to have a creator. If He had a creator, He would be created Himself and would not be the Creator of everything."
This question - similar to other questions that the people of doubt and desire ask, like "can Allah create a rock so big that He can't move it" - is a fallacious question and its premise is irrational, because it tries to apply the laws, attributes and conditions of the creation to the Creator.
Allah is The First and there is nothing before Him. His Existence is without a beginning, and He is uncreated. When we talk about "creation" we mean the creation of Allah i.e. everything that exists other than Allah, who is the Creator of all things. The idea of "infinite regression" is an illogical one and the mind rejects it for its impossibility. What makes sense is to say that everything has an origin, and this origin was there from the beginning and everything came after it.