what happens when that blood shoots onto rockys face?

I'm guessing you're speaking about the first Rocky movie. Well, basically Rocky's eye got swollen because of the punch he got there and he wasn't able to see through it because of all the swelling so he asked Mickey to cut out the swollen part. Mick used a razor and cut a hole in the swelling to release the blood. That way, the swelling is reduced.

I think you are talking about the scene when Rocky's eye is so swollen that he can't see so he asks Mickey to cut the skin to release the blood which will reduce the swelling enough to see out of his eye . . .

I think in boxing when someone's eye swells up the corner guys will cut round the boxers eye to release the blood which will reduce the swelling,i think