What if there's still a lesion after cryotherapy treatment for seborrheic keratosis?

Usually is. At least postinflammatory pigmentation. Keep an eye on it and repeat as necessary. These things basically don't ever turn malignant.

Related Questions

Does it take a few months for multiple seborrheic keratosis lesions to appear?

It may. Usually seborrheic keratoses appear over time and in an older population. If it is over a short period of time it may be something else but can be SK. If they look warty or 'stuck on' then that may be SK-but it could also be warts. If you are unsure see your doctor. Read more...