Is it necessary to fill the gap created in the row by the worshiper behind advancing, if the worshiper next to him moves a step?

The worshiper should fill the gap next to him if straightening the rows is obligatory, which is the view of some scholars, contrary to the majority who consider straightening the rows to be recommendable.

If the questioner is closer to the Imam than the person to his right, then the person to his right is required to move to fill the gap; because the Sunnah is for the rows to begin from behind the Imam and extend to the right and left, and being closer to the Imam is better.