Sea hares are usually simultaneous hermaphrodites that mate to reproduce. Egg-laying by a single individual is fairly rare and, from what I understand, is usually induced by either stress or aging. I've only seen one individual lay eggs in all the sea hares I've had over time. It is unlikely that the eggs are fertile and, but even if they are, the larvae would stand little chance at survival. I would take the eggs out (out of the display anyway) since sometimes sea hare eggs can contain irritants or other toxins and hungry fish can be rather dumb in aquariums. If you have a safe place to put the eggs away from other animals like a refugium, then you could always move them and see if anything develops.