the metal point of a pen 钢笔尖 
I dipped the nib into the ink and started to write. 我把钢笔尖蘸上墨水写了起来。
Oxford Collocations DictionaryNib is used after these nouns:- pen
Word Originlate 16th cent. (in the sense ‘beak, nose’): probably from Middle Dutch nib or Middle Low German nibbe, variant of nebbe ‘beak’.
