Arter had missed the Cherries' last two fixtures through injury and suspension before Saturday's win over Colchester, but was sent on as a first-half substitute after MacDonald suffered suspected ankle ligament damage.
The 22-year-old explained he was disappointed to see his team-mate sidelined, but added that he hoped to work his way back into Eddie Howe's starting line-up in the Welshman's two-month absence.
"The gaffer said at half-time 'let's win the game for Macca' because he's been magnificent for us this season," he told the club's official website. "He's been one of our best and most consistent players, so to lose him is a big blow.
"As much as I want to play, the last way I want to come on is because someone has been injured. He's a team-mate and a friend and I wish him well in his recovery.
"Being injured is the worst feeling and when someone comes in and does well, which will happen because of the quality we have in the squad, it's frustrating.
"You have to bide your time and take your chance when it comes, which is what I have to do now.
"I was in the team before I got suspended and then injured, and my aim is to get back in the team and keep the shirt."