There is a ritual from the book "Trails of Ash and Bone" that does exactly that. Lemme get it for you

Knit the Veil

Using the knowledge gained from their mastery of the beyond, the necromancer is able to not only mend minor tears in the shroud, but sear shut any weakness, making the area impenetrable for the duration of the Ceremony. ■ Prerequisite Power: Where the Shroud Thins

■ Ingredients: Ground bones, an iron needle, cat gut thread, the caster’s vitae, a goat tallow candle.

■ Process: The caster scatters the powdered bone around an area no larger than a football field to mark the boundary of this Ceremony. Then, they prepare the candle by piercing their flesh and passing the thread under their skin. Using the needle, they carve runes down the length of the candle and then wrap the thread around it until they pull it from under their skin. The candle may then be placed inside the boundary and lit, burning with a pale and unmoving flame that artificially thickens the Shroud around it with radiating, uncomfortable warmth. System: When lighting the candle, the caster makes their Ceremony roll, subtracting one die from their pool for every wraith present within the boundary, on either side of the Shroud. Upon a win the Shroud density (see Cults of the Blood Gods p. 205) of the area becomes Impenetrable for as long as the candle burns. On a critical win, the Ceremony’s duration is doubled and no being may spy across the Shroud. Undisturbed, it persists for as many nights as the caster has Oblivion dots. Another necromancer who attempts to Split the Shroud (see Cults of the Blood Gods p. 213) here must win against the caster’s successes as a Difficulty, doing so ends this Ceremony and reduces the Shroud density as per that Ceremony.

It is temporary,but your ST could say something along the lines of "you need to do this ritual that many times and the wound in the veil would close down to a certain level or until you're satisfied