Bell made 109 runs off 267 balls as the hosts set Australia a victory target of 311 at Trent Bridge.
"It's a great feeling to score a Test match 100," he told Sky Sports News. "You talk about it in the dressing room and it means a lot to everyone in the 11. It's a real proud moment.
"I certainly think in Ashes cricket it was [an achievement] and to play an innings like that in that situation, using some different skills on a slow pitch with a reverse ball, it was different and I really enjoyed it.
"With the ball reversing I was trying to play it as late as possible and the plan was to hit it as straight as possible and to time the ball short. You want to play it as late as possible and use the pace. It's been a brilliant Test match and today hasn't disappointed either. It's really exciting to come back tomorrow morning with all results possible."
Australia will begin day five on 174-6, requiring another 137 runs for victory.