We have a 2v2 soccer league. We use Fifa rules. One player hit a shot off the post and an opponent took it and started dribbling ball...?

Down the field. Another player was running back when the player on the ball cut in to score and accidentally clipped the leg of an opponent who was near him while running last him. However,they were both running parallel to each other but the attacker cut in and they both clipped each other, but only one fell down. Was it a foul or did the attacker score fairly.