Hamilton cut across the grass to rejoin the track and take the lead after a late decision to abort a pit stop.
Stewards took into account mitigating factors in a chaotic part of the race and issued a reprimand.
F1 rules dictate that “crossing the line separating the pit entry and the track by a car entering the pit lane is prohibited”.
Race stewards said that although Hamilton had clearly broken the rules on entering the pits, a reprimand was the “appropriate penalty”. Other possible punishments included a five- or 10-second penalty.
The ruling took into account that the driver and team admitted their mistake; that the offence was during a safety car period, when the speed of cars on track is controlled; and that the manoeuvre did not endanger any other drivers and was “executed in a safe way”.
His win gave him a 17-point championship lead over rival Sebastian Vettel.