While we do quality check each aligner, sharp edges are not uncommon. If you're experiencing gum irritation, you can buff and smooth out the edges of the trimmed aligner with a nail file or emery board. Be sure to buff parallel to the edge of the aligner, as filing perpendicularly can increase the roughness of the edge. It may a few tries before you smooth it down to the right texture.
If that doesn't work, take a small pair of scissors and trim any additional plastic that may be causing irritation. Trim carefully around the aligner, and do not go past the gum line.
If you are experiencing soreness, over-the-counter (OTC) pain medication can help.