The injury did not require an X-ray, but will continue to be monitored during training this week. The injury will not rule O'Driscoll out selection for Ireland's next pool game against Georgia on Saturday.
Out-half Ronan O'Gara bruised his left foot during the clash with Namibia, but its condition has improved over the last 24 hours and he is no longer considered an injury concern. The Munster man is expected to take part in training in Bordeaux tomorrow.
Prop Marcus Horan received a knock to his upper back during the game and has some muscular bruising in this area. He will not take part in training tomorrow, but is expected to be available for the weekend's game.
Meanwhile, fit-again centre/winger Shane Horgan has successfully completed a thorough rehabilitation programme, following the knee ligament strain he picked up last month, and he will take a full part in training this week. His scheduled recovery means he will be available for selection this weekend.
The Ireland squad were on a down day today with no training, but did have a pool recovery session in the team hotel. The starting team and replacements to play Georgia in Ireland's second Pool D match will be announced tomorrow afternoon at 3.30pm local time.