Sunday's match was set up by retired soccer player Stiliyan Petrov at Celtic Park to benefit a foundation Petrov set up after his battle with leukemia.
It was supposed to be a friendly match, but in the 53rd minute of the game, Agbonlahor tackled Tomlinson to the ground.
Tomlinson became ill on the soccer pitch and eventually had to leave the game.
Tomlinson's manager for the day, Martin O'Neill, said the pop star is fine.
"Agbonlahor smashed into him and he picked himself up and then was ill in the dressing room area, but he's not too bad now I think. He had to rush off but I think he's fine, he doesn't know where he is but he's fine. He was genuinely ill but he's okay now," O'Neill said.
Agbonlahor said he felt bad about the incident, which prompted the hashtag #PrayForLouis to trend on Twitter.
"It was one of those things. I'll apologise to Louis when we meet up with everybody after the game," Agbonlahor said.
Notable deaths of 2014 [PHOTOS]