My cat did this, and the way I got her to cover it up was to go and get
her whenever I saw that she had done an uncovered pile, and pick
her up while praising her and petting her and speaking soothingly, then
carry her gently to the litter box and very gently place her in it and
take her paws one in each hand and cover the poo that way.
She did not like this even though I did not make it like a punishment.
After just a few times she started covering it again. There were just
a few relapses over the next 20 years. Good luck!

get his

Some cats just won't cover their poop.  I just scoop it out
immediately.

As for the nail thing - take him to a vet and have his nails trimmed.
It should cost $10 or less.

Good luck!

-L.

Don't worry about it.  Some cats cover (& cover & cover & cover - spending
an inordinate amount of time doing it!), while other cats pee or poop, &
immediately hop back out of the box.  Then there are the in-between cats,
who use the litter box & then do a perfunctory job of covering.  They're all
different.  You can scoop right after he goes - or as soon as you notice it,
if the uncovered deal bothers you.

....and there's no way he would let me to get his

For this, you can make an appt. for the vet - or my guess is, even a
vet-tech - to clip his claws whenever needed.  Should be a nominal fee.  Or,
if you can manage to clip one or two claws at a time now & again, he may
eventually get enough used to it for you to clip them at home.

Cathy

I have a cat who for two years has diligently scraped the sides of the
enclosed litter box for up to twelve minutes after doing business.  Didn't
cover anything.  Just made a lot of noise.