BLUE TONGUE SKINKS

So I recently ordered a Northern Blue Tongue Skink from KO Exotics. He arrived happy, healthy, and very curious. He had absolutely no fear at all, he'd come out and stare us down, wonder what we're doing, respond to us talking to him, and he's even eaten treats straight of my hand. He eats every day, even now. We started handling him about 3 weeks in, it went very well. He only bit me once and that was when he was trying to figure out what my hand was. (he thought it was food) He's let me pick him up the last 2 times. Then suddenly about 6 days ago he started hiding from us, any time someone comes into the room he runs and burrow, he'll only eat if he's alone in the room, and the only way I can coax him out is with the tongs (he knows tongs mean food and he tries to bite them). But even then tonight he flinched at the tongs when I was putting some food in. I'm starting to get a little worried about him

Also he shed last week so I don't think his behavior is because of that.
Pic attached of him, his name is Baja Blast

i forgot to mention, one of those days i was just walking by the glass and he started heavily hissing at me which he's never done. i figured he could have been grumpy but with everything else

At times when temps go up a bit they can get a bit jumpy. Has that happened lately?
Do you have other pets that may have frightened him? They can get irritable, just like we can sometimes. I've got some pretty moody split-personality ones myself.

No other pets and I regulate his temperature pretty well.

It's still a young skink and they're easily spooked. Give it some time and as long as your husbandry is correct, no need to worry. Even "teenage" and adult skinks can become temperamental at times. I had a skink that just recently passed that I owned since a child, and every now and then would inexplicably gape its mouth at me when changing the food.