Some blood from slaughtering the sacrifice got onto his ihram garments

If the blood is pure (tahir), it does not matter if it gets on to one’s ihram garments or other clothes. Pure (tahir) blood of an animal is that which remains in the flesh and veins after it is slaughtered, such as blood in the heart, legs and so on. But if the blood is impure (najis), it must be washed off, whether it got onto ihram garments or anything else. This refers to the blood that is poured forth. So if someone slaughtered a sheep, for example, and some of its blood gets onto him, then he must wash off the blood that got onto him, regardless of whether it got onto his clothes or his ihram garments or his body. However, the scholars (may Allah have mercy on them) said that a small amount of blood is overlooked, because it is difficult to avoid it. End quote.

Majmoo‘ al-Fatawa by Ibn ‘Uthaymin (22/11).