Lower, early leaf? 1 serrated blad or 3? I won't worry about that one. The rest of the plant looks great in your diary.
As long as it isn't a "tunneler" pest and just a blemish, nothing ot be concerned bout. Those early leaves often have such a blemish. i have one that is slightly less prominent, elongated pale spot (wihtout the dots like oyurs) but large nonetheless, but the young plant is healthy otherwise. No problems on other leaves, and the spot isn't expanding (i.e. not a pest).
As the oldest leaves get covered, they may not be as pretty over time. molting, blemishes, and even dropping the leaf altogether is likely at some point even with a 100% healthy plant.