What is this???

Ella

Today my daughter spent a few hours being babysat by my sister in law and when i took her home i saw these on one of her legs, what is this???

I know she put her outside on grass earlier to play but thats all, its freaking me out. Its just purple spots. She doesnt look bothered by it and it doesnt bother her when i touch it at all. Its only on one leg. Everywhere else is fine.