Very frequently used word in Mandarin that sounds like "nica" or "nigah"
The word your hear is probably 那個 (in traditional characters) / 那个 (in simplified characters). It is pronounced nàge or nèige (in the Pinyin transcription), and it's basic meaning is ‘that’ or ‘that one’.

Chinese Grammar Wiki has a nice explanation of how nèige is used as a filler word (follow the link to see examples):


  In conversation, you may find yourself at a loss for words, unable to find the correct phrase you are looking for, or simply needing time to gather your thoughts. When you experience this feeling, in English, you may say "umm" or another filler word. In Chinese, the word for this is 那个 (nèige). (The word 那个 can be pronounced both "nàge" and "nèige," but for this usage, "nèige" is normally used.)