The New Zealander, 31, submitted an early guilty plea to the Rugby Football League for his part in the clash.
Flower faces a tribunal on Tuesday, and is facing a minimum eight-game ban.
Flower punched Hohaia to the ground and then landed a second blow to the face of his opponent as he lay on the pitch.
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Police are investigating the incident, but have not received any complaints from members of the public.
However, they will continue to liaise with relevant parties - including the Rugby Football League, the Criminal Prosecution Service and St Helens - before deciding on a course of action.
Hohaia had been charged with a grade B offence of striking, which normally carries a ban of one or two matches,
But because of his previous record, Hohaia was entitled to submit an early guilty plea to receive the smallest sanction and avoid a hearing.
"Lance Hohaia has accepted the EGP and will miss the first warm-up game of next season," a St Helens spokesman said.
Saints have also announced that forward Richard Beaumont has left the club - he failed to play a game after joining on a two-year deal from Hull KR.
St Helens half-back Lance Hohaia has accepted a one-match ban for striking Ben Flower with his forearm during the Grand Final, in an incident which led to the Wigan prop's sending off.