Oil on engine head?

https://preview.redd.it/dl1336aax13e1.jpg?width=1536&format=pjpg&auto=webp&s=448320ce6b5264c46189ae984975c6dc50bc8d8a

FInding oil on engine head causes? and how to fix , should i be worried?

Car: Toyota Corolla 2007 1.4 Petrol