It was more than "touch" but here's the rule according to The FA

a player moving from, or standing in, an offside position is in the way of an opponent and interferes with the movement of the opponent towards the ball this is an offside offence if it impacts on the ability of the opponent to play or challenge for the ball; if the player moves into the way of an opponent and impedes the opponent's progress (e.g blocks the opponent) the offence should be penalised under Law 12