In Ant-Man and the Wasp, Scott enlarges inside a room in the school. Instead of breaking the walls, he curved his body along the corners of the room

Since Thanos’s skin was barely scratched by a high-tech suit in Infinity War, then it’s unlikely that Scott’s body itself would wound Thanos’ rectum. It’s more likely that Scott will become insta-mushed-poop for Thanos to defecate unwillingly like a bad diarrhea

That could help other heroes in battle though, since it would certainly numb Thanos in discomfort for a few seconds… however we don’t trade lives