Albert Barnes on John 1:43

Would go forth.

Into Galilee. He was now in Judea, where he went to be baptized by John. He was now about to return to his native country.

Findeth Philip. This does not refer to his calling these disciples to be apostles, for that took place at the Sea of Tiberias (Mt 4:18), but it refers to their being convinced that he was the Christ. This is the object of this evangelist, to show how and when they were convinced of this. Matthew states the time and occasion in which they were called to be apostles; John, the time in which they first became acquainted with Jesus, and were convinced that he was the Messiah. There is, therefore, no contradiction in the evangelists.