Q: Ok, so i need to know tis. how much blood is permissible on a person when praying salaah? I ask due to a cut i had and did not notice it until after salaah and the salah was over and i noticed it.

A: Under ideal conditions, no blood of any type should be smeared on clothes or body. The books of fiqh does give the following concession due to circumstances that may be imposed upon a person that would reduce them them ability to remove all impurities — be it knowingly or unknowingly:

Whosoever is contaminated by severe filth, such as blood, urine,
stool, or wine to the amount of a dirham or less, salaah is permissible
with it. However if it is more it is not permissible. (Kindly see Muktasar Quduri)

Allah certainly Knows Best.

p.s. Glance at the following to better understand the matter of purity, after all, purity is part of faith.