The batsman tried to catch a Matthew Bell shot and put his hand up to protect his face. The ball hit his hand and Bell crashed to the ground.
Bell was taken to hospital, but returned just after lunch with his arm in a sling and a diagnosis of nothing broken but a badly bruised arm, following an x-ray.
He may take some part in the match.
Warwickshire batsman/wicket keeper Tim Ambrose is in the England team which are currently fielding and caught McCullum off the bowling of the bowling of Ryan Sidebottom for 51 .
At the close of play, New Zealand were 282-6.