Why is alar rim graft needed only on one side of nose when my nose was symmetrical before? Will it make alar stiff? (Photo)

A cartilage bump on the left of my nose tip.Doc says i will need an alar rim graft on the left side. He said its not a bump, it’s basically because on the left there is not enough lateral cartilage? Also he said maybe a graft was put there thats why its like that.My question is. Why was the graft even needed in the first place (wasn’t discussed pre-op), did he accidentally remove more than necessary cartilage from the left side of my nose tip?Because I didn’t have any issues with symmetry before