iOS Photos app: Inappropriate photo on People & Places section under Albums
Assuming this is coming from "people" and not "places"
In Photos, tap on the "People" and scroll until you find that person. (It may be aonther picture than the annoying one) Tap on the person and then tap the "..." in the top right corner. Then select Remove from People Album.

If that is too drastic, "Unfavorite This Person" might work if they are showing up because they have been favorited."

Finally, if neither of those works, (or you don't want to do them), you can open Photos on your mac (assuming you have one) and see if the image still exists there to be deleted.