A few things here
I just got my first hognose last Saturday, a green phase male who the breeder told me is almost an adult (forgot to ask for his hatch date). Anyhow, he's already eaten for me (a fuzzy) earlier this week so not worried about that. I'm just wondering about his behavior.
Given the size (judging by your hand) he should be eating something bigger than a fuzzy mouse (I have 20 grams hatchlings from this year eating fuzzies already), ideal prey is 1 to 1.5 time it's girth size every 5 days., once they are about a year you can decrease to one feeding a week. Avoid rats, rats are fatty and Hogs are prone to fatty liver diseases.

but he has not burrowed as far as I can tell. Every time I've come in and he's not nosing the top, he's just laying on top of the substrate.
While they should be provided with a nice layer of substrate to burrow not all do, adults tend to do it less and less as they mature, they still do it but not as much as adult so it's not abnormal.

So long your temps are not falling below 75 and reach around 90/92 on the warm side he will be fine.