If he/she don't pee thru it, then its a clit.
Some kids arew born with sexually ambiguous genitalia like this.
As the clit gets larger, it naturally starts to look more and more like a dick because its the same tissue that forms a dick in embryonic development.
Although it LOOKS like it has a slit... that could just be a cease in the head.
As mentioned,tho... this could also be the result of testosterone use.
It could be a female looking to transgender to a male... hence the hairy knuckles.