The Ghanaian midfielder hit a low left-footed drive from 25 yards in the eighth minute which flew past Stefano Sorrentino in the Chievo goal.
But the goal did not ease the nerves of the visitors who had picked up just one win in four games coming into the match as Chievo began to dominate possession against a lacklustre Milan.
In particular, Cyril Thereau's probing runs in behind were not picked up by the static Milan defence and after 25 minutes he was found by Alberto Paoloschi. The French midfielder hit a low strike at goal, but Christian Abbiati was on hand to make a smart save with his legs to deny the home team.
Abbiati was on hand to make another fine stop at full stretch on 42 minutes as Sergio Pellissier's low drive from 25 yards was thwarted.
Three minutes later, Cheivo had their best chance of the half as they broke down the right hand side through Pellissier, his pull back found the unmarked, onrushing Luca Rigoni who drove the shot wide from the edge of the box.
Chievo's domination of possession and territory left them liable to Milan counter attacks and Antonio Nocerino could have doubled the visitor's lead in the 28th minute as he looked to latch onto a Mattia Scigio clearance over the top. However, his first touch was a heavy one and Sorrentino was alert to gather the ball.
Zlatan Ibrahimovic and Robinho were left increasingly frustrated up top for the visitors and the visitors had to wait until the 36th minute for the first meaningful contribution from the duo. Robinho swivelled his hips to outfox two defenders and to put himself in on goal, however, his low shot was again by Sorrentino's legs.
The second half continued in a similar fashion.
In the 50th minute, after patiently keeping the ball, a deflected cross from the left fell to Pellissier who hit a clean, low volley which was straight at Abbiati. A yard either side and surely Chievo would have had their equaliser.
Just a minute later Pellisier squandered another opportunity as he poked a Michael Bradley's pull back over from eight yards.
Milan were thankful for the referee's assistant's flag in the 80th minute as Thereau's flick hit the hand of Nesta inside the box, but the certain penalty was not given as the French midfielder had run from an offside decision.
Francesco Acerbi then was correctly flagged offside after he momentarily thought he had scored with the last kick of the game.
The full-time whistle sounded moments after to the relief of Massimiliano Allegri as his Milan team moved top of Serie A after picking up an undeserved - yet potentially crucial - away victory.