As Roger says, filed a bit off the left side. That will make the sight's centre be more to the right, which is the same as moving the sight to the right, making you hold it over to the left, therefore the shot will now fall to the left, where needed - or, you could bend the barrel to the left just a bit. 2" isn't much and I'd try moving the sight first, either by removing and replacing it a bit to the right, or filing if it has enough width/thickness.
A thin blade on a trade gun makes for a very good sight picture. A short angle on the rear, polished, shows up well in the bush- just like a beacon. For shooting light coloured targets, sight-black or a felt pen works well & wipes off with your thumb.