@ Naomi: Hemorraging (ie, ruptured blood vessels) to a deadly extent while helping an egg is unlikely. The reason people do not handle eggs that are actively bleeding (and stop working on them when they are helping) is to keep from nicking another vessel while peeling at shell and membrane. However, simply handling/holding the egg should not cause additional bleeding or vessel ruptures.
@BLaBauve: Some visible blood may be seen without too much cause for concern. Sometimes chicks will pip a little earlier than they are physically ready to, and there may still be some blood in the veins of the membrane. If a bird pips through a vessel, they will most likely bleed to some degree, but if you leave the egg alone it should be able to stop on its own. In fact, it should already be stopping by the time you see blood and like Sonja said, the only cause for concern is when it's clearly flowing out instead of seeping or just being present. Good luck with them!