O'Driscoll was taken to hospital for an x-ray and now must await the results to discover whether he needs surgery.
Leinster slipped to sixth in the Magners League with defeat away to champions the Ospreys and will be without O'Driscoll when they return to Wales to face second place the Scarlets on Friday.
"He's going for an X-ray and could have a crack in the jaw, the treatment for which we're not sure yet," said Ireland coach Declan Kidney.
"If it's just a crack, he might be able to avoid surgery and having a plate inserted. We'll just have to wait and see what the story is there.
"He felt okay; it just felt prudent to get him off when we did. Brian felt comfortable himself, he asked for a few minutes but the medics said he had to come off."
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