NEED ADVICE! 5 years old has high fever and no other symptoms

He played outside in the morning (it was about 90 degrees), then he came home saying that he is dehydrated. I gave him some water and he layed on the couch to watch some cartoons.
Later I came and checked on him, he was hot to the touch, his temperature was 102.
He also felt nauseous, but didn't throw up.
I gave him some getarade and water. He was pretty achy, then He went to sleep, but his fever is still fluctuating between 102 and 104. I called a nurse, she said to just watch him and call my doctor if fever goes higher than 104.
I don't like dragging sick kid into doctor offices just to be told to keep an eye on him. And neither do I like giving him tylenols or other over the counter things needlessly. (i do have them in my cabinet though).
I did give him some water with kids magnesium in it.
He doesn't have any other symptoms (so far). His tonsils are swallen (for few days now), but he says they don't hurt.

What do you think it is?
If it's a heat exhaustion, wouldn't his fever go down by now?
Could it be flu or virus? But where are other symptoms?
What would you recommend doing naturally. I have many natural things at home.
Olive leaf tree extract, Colloidal Silver , oil of oregano (undilluted), etc...
thank you

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