Praise be to Allah.
The scab that forms over the wound is usually something insignificant that can be overlooked, especially if a person is frequently exposed to wounds and scabs like this form on them.
It says in Haashiyat al-Baajoori ‘ala Ibn Qaasim (1/51): It is obligatory to remove any barrier that forms on them, such as dirt that accumulates from the outside, if it is not too difficult to remove it. Otherwise it does not matter, because it has become like part of the body … This applies to the surface of boils, even if it is easy to remove it. End quote.
In other words, this surface or skin does not have to be removed, even if it is easy.
It says in Mataalib Ooli an-Nuha (1/116): A small amount of dirt under the nails and the like does not matter, such as what may be inside the nose, even if it prevents water from reaching the skin, because it is something that usually happens a great deal, and if wudu could not have been sound with it, the Prophet (blessings and peace of Allah be upon him) would have explained it, because it is not permissible to delay giving an explanation from the time when it is needed.
Shaykh Taqiy ad-Deen Ibn Taymiyah (may Allah have mercy on him) made an analogy between that [a little dirt] and every insignificant thing that prevents the water reaching the skin, such as (congealed) blood or dough on any part of the body. He favoured this view by analogy with what collects under the nails, and also included with that cracks that may appear in the skin on any part of the body. End quote.
See the answer the question no. 223873 .
The fact that this may be overlooked in order to make things easy and avoid hardship is because many people are affected by such things and it is too difficult to avoid them. This ruling applies to regular cases when there is no waswaas. However, if a person is affected by waswaas and he checks himself constantly and repeats prayers because of that, then what the one who cares for himself must do is ignore that altogether and not think about it, otherwise it will spoil his worship and cause him too much trouble, as you have seen how the Shaytaan has caused you to go to extremes in this issue, and has made worship burdensome for you by causing you to repeat it frequently, when there is no shar‘i reason to do so.
And Allah knows best.