My son had a similar thing with a temp that went away and came back after 12 hours. I did take him to hospital last night because his pulse and breathing were too fast and they were really great about it. Better safe than sorry, if you are worried get him checked out.
If in doubt I have found the nurse on call phone line to be awesome. That was in Victoria though- depends what state you're in as to whether you have one, and what it's called. Hope he's better soon!
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