In league of legends, most people say Nocturne is a jungler, but I'd like to know if its possible to play him as a solo top.
Nocturne's sustain from his passive is not on the same level as sustain from other tops such as Vladimir, Olaf, Irelia, Lee Sin, etc. This is the first negative for him: he would lose trades vs any of the more reliable "normal" top champions.
Additionally, Nocturne's ability to sustain revolves around him autoattacking continuously to lower the CD on his passive. On top of that, the passive heals him based on how much AE dmg his next attack does. These two issues combined will have your lane pushed to their tower 24/7, which means you are open for ganks even if you are you vigilant about warding. Since most junglers have gap closers, it is difficult to retreat from their tower in top lane to yours even if you start moving as soon as your ward sees the enemy jungler.
Essentially, even if you are winning vs your laning opponent(which is already unlikely!), Nocturne's kit is such that you are left wide open to being ganked - repeatedly.
For the reasons outlined above, and probably some I am missing as well, Nocturne works best in the jungle where his passive sustain can be used freely without having to deal with the negative aspects of it.
Yes, but it's probally not the best idea. He will likely auto-push the lane with his passive. Push too far and you can get (easily) ganked