Ironing will dry out the emulsion and cause warping if heat is used, while cold flattening will not remove the creases caused by trampling.
It is not too difficult to apply 'equal and opposite' bends to the film base along the line of the crease while gripped between forefingers and thumbs. I then place the film onto a firm, but giving, support below it, a mouse-mat for instance. I then place a protective sheet of acetate above the film and use a 'smoother' made from an old ivory or bone knife handle. Firm pressure along the line of the crease will remove the crease and conform the film base back to being flat. It is important to keep the wound film coils flat as un-smoothed creases will abrade the emulsion, and including rubbing the adjacent coils above and below the crease.