From Irish Times:
O’Connell made contact with Kearney’s head while kicking the ball during the second half of the match in Limerick, but after reviewing video footage of the incident the citing commissioner, Eddie Walsh, decided the second row does not have a case to answer.
It was felt that although O’Connell’s shin came into contact with Kearney’s head, the player was making a genuine attempt to get the ball and there was no deliberate intent to kick the Leinster winger.
I agree it wasn’t deliberate but I did think he might have been cited for dangerous play