Nikhil is Hindu and it mean 'complete, whole, entire'
Pranav is Hindu too and it means 'symbol'
Najee is Arabic and is a variant of
Naji' (it means 'useful, beneficial')
Nicklaus is from
Nicholas and it seems like a Cornish version of
Nicholas (the surname Nicklaus was first reported in Cornwall and many people that bear that name still live there)
Nathen and Nathanial not necessarily modern spellings, but just variants
that's it :-)