Jeff Hughes headed County in front inside the opening two minutes, but Kiwomya's side were dealt a major blow on the stroke of half-time when Andre Boucad was sent off after picking up a second booking for a trip on Harry Arter.
Bournemouth striker Brett Pitman scored for the sixth game in a row while in-form Matt Ritchie cored twice as the Cherries maintained their grip on second place.
County have now won only one of their last seven games, dashing any lingering hopes of a late charge for the play-offs.
Kiwomya said: "I'm very disappointed with the referee. I thought he spoiled the game.
"It could have been a very good game between two attacking teams, but he's giving out yellow cards. Their second goal followed a handling offence.
"We started off well. The goals we conceded could have been avoided.
"Playing with 10 men, it was a mental battle. It was a backs-to-the-wall job, but we played well and created chances. But you have to take them.
"If your not solid and determined, you could go down by five or six, but the lads stuck to it and were magnificent.
"I wanted to try and win the game, but then they scored their third goal."