The former Derry City winger sent a derogatory tweet about a Northern Irish newspaper over the weekend which was later deleted.
McClean has landed himself in hot water with his use of Twitter on several occasions, prompting former club Sunderland, who were managed by O'Neill at the time, to twice ban him from using the social networking site.
His fellow Ulsterman is now in charge of the Republic and was already considering imposing new rules before the latest incident.
Speaking on Poznan, where Ireland play Poland on Tuesday evening, O'Neill said: "I wasn't overly pleased.
"James seems to enjoy the Twittering and his performance merited one or two tweets from other people saying how he had done, rather than James getting embroiled again.
"It all leads to the whole thing again about the tweeting. I think even before I arrived here, there was a matchday ban on tweeting - in fact, it might even have been a matchday minus-one or plus-one, as the case may be, or even a two-day ban.
"I am just experiencing these things again, so let me have a look. I don't want to be a guru over this social media and players. I think there just has to be a bit of responsibility.
"Sometimes I think the players don't realise, even after all this time - maybe they do, maybe that's my view - they might not realise that this is a public media and anything they say is just picked up."
O'Neill was asked if he had spoken to McClean about the matter, and while he acknowledged that he had, he defended the player to a degree.
He said: "I have reminded James. But remember, it's a fairly lengthy time since I last mentioned it to him. There has been a lot of tweeting gone under the bridge since then."
Ironically, the Wigan midfielder turned in one of his better performances for his country in Friday's 3-0 friendly victory over Latvia to earn headlines for all the right reasons.
However, O'Neill, who plans to make changes for the clash with the Poles, said the Twitter row would play no part in his selection.
He said: "If I am going to leave players out because they have tweeted, then I am going to be in serious trouble down the line. That's kind of a semi-joke.
"If James doesn't start, it won't be anything to do with tweeting. But I still have to have a word."
O'Neill revealed he has had no requests from club managers to rest players for his second game in charge, but insisted he is keen to have a relationship with them having experienced life on the other side of the fence.
He said: "No, I haven't, not one thing, not a soul. No one has sent any messages out saying for someone to play a half or something like that.
"Of course, even at this early stage, I wouldn't mind, really, getting a decent enough rapport with club managers.
"I know from past experiences, I would have actually appreciated an international manager calling me to say, 'Listen, it's the second game, I might only play one of your players for, let's say, the first half, or something like that, in the game'.
"All those things were greatly appreciated at the time, so I don't see why now, since the positions are reversed, that I shouldn't listen to the same.
"But no one has actually called."