I was wondering if sucking your own blood or biting at your own scab or otherwise consuming yourself was halachically permissible, since, as far as I can tell, humans are not kosher. Even so, it would seem that autocannibalism in some form or another is basically unavoidable and I have never heard of it being prohibited.
"Human blood, if it is separated from his body, is forbidden because of appearances (maris ayin). Thus, if one bit into a piece of bread and blood came out from his gums onto it, he must scrape that portion off. On the other hand, if it is still between one's teeth, he may suck it out."
Rashi to Kerisus there explains that the essential distinction isn't really between whether the blood is visible to others (as on the bread) or not (as in the gums), but just whether it is separated from its place of origin. So it sounds like sucking any kind of wound would be okay under the laws of kashrus, although there might be the consideration of "bal teshaktzu" - not eating disgusting things (Yoreh De'ah 116:6).
Alex beat me by a minute here, but nonetheless:
The Talmud talks about all sorts of things!
Interestingly enough, the Biblical prohibition on non-kosher animals doesn't apply to humans. (Hence, all human milk is theoretically kosher.)
However if you have a cup of blood sitting on the table here, the rabbis of the Talmud said don't drink it. Even if it's human blood and theoretically not prohibited, people would think you're drinking cow blood or the like (which is Biblically prohibited). So the rabbinic prohibition kicks in if the blood has separated from the host body. Hence:
כדתניא דם שעל גבי ככר גוררו ואוכלו שבין השינים מוצצו ואינו חושש
If you find [human] blood on your bread, scrape off the blood and eat the remaining bread. If there's blood between your teeth, suck on it all you like.
I posted an article here in which the conclusion I came to was that in many circumstances it can theoretically be permitted to consume human blood. While the purpose of that article was to be humorous (it was Purim time) I think the argument is technically pretty sound.