We can't be certain, as symptoms from several causes can look nearly identical, but this spotting resembles damage from a virus. Probably a mild infection as viruses go, given its  apparently limited impacts thus far, but plant viruses are incurable and will eventually systemically infect the entire plant, so trimming out symptomatic areas won't be very beneficial. You can certainly continue to harvest what you can if you wish, but the plant may decline before the end of the season. Otherwise, the plant needs to be removed and disposed of (do not compost). Viral infections are not an uncommon problem when growing pepper plants, and several kinds of insect can spread the virus from plant to plant, though insecticides are not useful in preventing this. Keeping weeds away from the garden will help limit what alternate food sources those insects have, since those plants might harbor the virus that the insects brought into the garden. Even so, flying insects can bring a virus into an area after having fed on infected plants a much greater distance away (miles, possibly).

The other possibility is a nutrient deficiency, particularly with either iron or manganese. Low levels can manifest as spotting/mottling of yellow areas, and always occurs on younger foliage first. If you have fertilized the plants recently (with a balanced fertilizer which includes these nutrients), this is not likely the cause. Similarly, if the mottling progresses or impacts the developing fruit, then nutrient deficiency is not the cause, and virus remains the most likely culprit.

Miri