Nihil est incertius volgo - Nothing is more uncertain than the (favour of the) crowd. (Cicero)
Nihil est miserum nisi cum putes - Nothing is unfortunate if you don't consider it unfortunate. (Boethius)
Nihil est--In vita priore ego imperator romanus fui - That's nothing--in a previous life I was a Roman Emperor

Nihil obstat

Nothing stands in the way

Nihil sub sole novum - Nothing new under the sun
Nihil tam munitum quod non expugnari pecunia possit - No fort is so strong that it cannot be taken with money. (Cicero)
Nihil - Nothing
Nil actum credens dum quid superesset agendum - Thinking nothing done, while anything was yet to do
Nil actum reputa si quid superest agendum - Don't consider that anything has been done if anything is left to be done. (Lucan)
Nil admirari - To admire nothing. (Horace)