Should I report this as my asset? Or should I just ignore it?
I think it has to be according to the tax law of your domicile.
If you don't report your asset, would it be treated as tax evasion?
That is the question that you would ask yourself.
He seems to be worried about IRS as mentioned by the other folks above, he shouldn't worry if he's still keeping the 1 bitcoin he had. Each country has different ruling about taxation.
But as long as he takes it as 'profit', then he should report and comply to be worry less.