Welcome to the Amaryllis forum
I think that the bulb is just fine. Sun scorch would show up on the whole leaf. From the position of nearly a straight line across the leaves, it looks as if something happened before the leaves emerged. I wonder if there was some trauma to the bulb in storage or shipment that could have caused what you see. If this doesn't spread up the leaf, I think it is just cosmetic. Fungus gnats are a real pain, and the eggs could have been in the potting mix. Gnats will spread to your other houseplants.
There are lots of home made treatments for controlling them, such as fly strips and watering with dilute hydrogen peroxide. But it is better to start out with a good potting soil and keep the soil as dry as possible, since the adults are attracted to fungus in the soil, where they lay their eggs. Please post a photo of it in flower when the next scape blooms, since we all enjoy seeing the different varieties.