Angry fans at Djurgarden's home stadium in Stockholm threw bottles, coins, fruit and other objects onto the pitch as Mjallby's players celebrated a goal in the 37th minute.
Television footage showed Mjallby defender Gbenga Arokoyo falling to the ground after an object hit him in the stomach. Swedish broadcaster SVT said it was a pear.
Arokoyo said after the game he was in pain but not seriously injured.
The referee and his assistants decided to abandon the game after a meeting with police and representatives from both clubs. It wasn't immediately clear when and if the match would be resumed.