Will's knee is looking much better. Laura took him back to the pediatrician Saturday and that doctor said she thought it might be from a bug bite. But at that point, we could see that the swelling and redness had gone down from the line I'd drawn around his boo-boo. The medicine seems to be working. I don't think it's going to abscess - the redness is almost gone at this point.
His face and head is, however, now covered in purple fingernail polish that gives a "deep, wet" look - it will probably be in his hair the longest. Many thanks to the yellow-haired child, who used the rest of the polish on the outside of the house and saved a tiny dab for the cat.