Why am I getting pinching on my mesh?

In most cases, you get a pinch because of your normals of the mesh. Just recalculate them by pressing F3 > recalculate outside/ inside.

The problem is that you have one long edge connecting the upper and lower vertices, as well as several shorter edges in the same place.

Select the long one, and remove it, and the problem will go away.

To select it, you may have to click several times, to alternate between the long one and one of the shorter ones. Once the long one is selected, remove it by pressing X followed by E.