My lizard has a white spot on its head. Is it retained shed? Home care?

Thank you for your question about Loki, and thank you for the photos - they are very helpful! From what I can see in the photos, I think that you are asking about the large white area that extends from the eyes forward to around his nose and down along his mouth. This looks like areas of retained shed on top of new skin. Difficulty shedding, or dysecdysis, is often the result of imperfections in the husbandry. I would recommend starting with soaking Loki in 85-90 F water once daily for 15-20 minutes. While in the bath, you can wet a paper towel or cloth and get the areas of retained shed wet. Use caution around his eyes and nose, however, as we don't want him to feel uncomfortable or panicked.
I would also suggest evaluating the husbandry and diet closely. You can consult an online care sheet, such as anapsid.org or Reptiles Magazine, and see if there are any areas that you may need to make adjustments. Common areas that require adjustment include lighting (UV lights need to be changed every 4-6 months), temperatures, and humidity/hydration/water.
I would also recommend taking Loki into a veterinarian at some point for a wellness examination. Your veterinarian can make recommendations that are tailored to Loki after his physical exam has been performed.
I hope that gives you a place to start, and thanks for using Petco Pet Education Center, formerly Petcoach!