title_body: IPA for Voiced Velopharyngeal Stop?
upvoted_answer: What I think you meant to ask is to create a stop consonant by stopping air flowing through the nasal cavity while the mouth is open, then releasing it only through the nose while the mouth is closed.
  
  The problem is that having no airstream block in the mouth can mean one of two things: producing an oral vowel, such as /a/, or making no sound at all. There isn't a plosive-like sound for stopping air flowing through the nose, as there is with the mouth (in multiple places). The way you can test this is by producing a sound like /aãaãaãa/, in which you are repeatedly stopping the nasal airflow, and yet the vowel sound remains continuous because there is no stop of air in the mouth. So a stop created solely by blocking the nasal passage is impossible.
  
  The example you give for this sound is [ĩɲ't̚?ⁿn̩], where the [?] is supposed to represent the unknown sound. This has a [t̚] with the diacritic for no release after the consonant, and a nasal release [ⁿ] after it. However, there can't possibly be anything between [t̚] and [ⁿ]. The [t̚] means that when the consonant ends, you are still blocking both oral and nasal airflow, and the [ⁿ] means that you are releasing nasal airflow while keeping oral airflow closed. There is no articulation possible in between these: if there were an oral release, the diacritic on [t̚] would have no meaning, and there could no longer be a nasal release [ⁿ] after it. The only possibility is to add another consonant, or extend the [t] as a long consonant [tː], which continues to block all airflow.
  
  Going through your definition, nasal release seems to fit (another possibility that fits just as well is a pre-stopped nasal, if the nasal consonant is supposed to be more prominent than the stop):
  
  
    This stop is formed by stopping air from flowing into the nasal cavity with the velum 
  
  
  Stopping airflow is a property of a stop consonant. A stop consonant stops the airflow in the mouth as well as the airflow in the nasal cavity. (Stopping only the airflow in the nasal cavity is impossible here, as explained above.)
  
  
    while the mouth is in position to form the following consonant
  
  
  Simultaneous articulation is possible, but it depends on what the following consonant is. If the following consonant is in the same place of articulation, that means there's no change.
  
  
    and then releasing it into the nasal cavity.
  
  
  Releasing the stop only in the nasal cavity means producing a nasal sound. Nasal release (and nasals in general) would continue to block the airflow in the mouth, but allow it to pass through the nose.