Blimey.
Kitten needs to be kept warm and still, assess amount of bleeding (eg is wound oozing, dripping, constant trickle or more?), keep it as clean as possible, cool it to contract blood vessels, keep it above heart level (eg head down) if the kitten will let them - which would in itself be a sign that all is not well cos a 16wk kitten shouldn't cooperate with that.
If it's doing more than oozing and/or hasn't stopped after 20mins the kit definately needs vet.
If kitten shows signs of shock (abnormal behaviour, kitten collapses or won't wake up properly, gums very pale or white instead of healthy pink) then its also definately a vet job even if bleeding is stopping.
If lots of blood is being lost (more than a trickle) then kitten needs vet NOW.