England require a further 332 runs for a victory on the fourth day.
Root suffered the injury in the 18th over of India's second innings while attempting to catch an edge from Shubman Gill in the slips.
The delivery from Tom Hartley was played with hard hands by Shubman Gill resulting in a thick edge that flew towards the left of Root in the slip cordon. Root managed to touch the ball with his finger but couldn't complete the catch, and the ball went for a boundary.
"Joe Root sustained an external blow to his right little finger, attempting a slip catch in the first session of D3. The England medical team will keep him off the field for the time being to treat and ice," England team management said in an update.
Anderson said the team management didn't want to risk an external blow, hence Root didn’t return to the field.
"Yeah, he's just been looking after it basically. He took a knock on it this morning in practice I think. He then took one in the field as well. I don't think there's concern. Just making sure it's as good as possible for tomorrow. There's a chance we will need him with the bat. So it's making sure he can hold a bat.
It's making sure he's as good as he can be. There's no point risking it for an external blow, no point risking it further out in the middle, so it's making sure that he's good enough to bat," Anderson said during the post-day press conference.
England are chasing history as they have been set a target of 399 runs to win the second Test and they ended day three on 67/1, still needing 332 runs for a victory on the fourth day.
(PTI inputs)