Previously, when it got blocked, it took several days and hours of meditation to reopen it. Recently, with emergency measures, it can be reopened within an hour, and with a few hours of meditation per day, it recovers to some extent.

When this area gets blocked, it becomes quite critical, and consciousness becomes chaotic and hazy. However, even if seated meditation is difficult, focusing consciousness and intending to open that area can open it to some extent. At that time, I feel that if I put my palms together slightly apart in the center of my chest, like a Qigong form, it becomes easier to cultivate energy, and an aura tends to gather in the forehead. By doing so, the Nadis (energy channels) around the nose are opened.

Originally, this area was open, so even if it closes, it is relatively easy to open, and there is not as much difficulty as when opening it for the first time.

When I look around, surprisingly few people have this area blocked. In my case, it seems that bullying and being yelled at during childhood, and rejecting people with such a temper, caused a feeling of rejection, and that feeling of rejection may have been the cause of the blockage in the Nadis (energy channels) from the nose to the forehead.

The order was:
Bullying/yelling → Shrinkage/rejection of people with bad temper → Blockage of Nadis from the nose to the forehead.

It took a surprisingly long time to resolve this, but I think it was because I wasn't even consciously aware that there were Nadis in this area, and because of that lack of awareness, it was put off.

The order seems to be:
Relaxation of the entire head → Movement begins in each part of the head → The energy channel (Nadi) from the throat (Vishuddha) to the forehead becomes stronger/thicker → Similarly, the energy channel (Nadi) from the forehead to the back of the head becomes stronger/thicker → An energy channel (Nadi) begins to form from the back of the head to the crown (Sahasrara).

In terms of the percentage of how clearly the channels are formed, it is approximately:
Throat to forehead: About 50%?
Forehead to back of head: About 30%?
Back of head to crown: About 10%?

In reality, I don't know what a completely open state feels like, so the range may be different, but the percentage is about this.