I would think burn but yes it probably is toxic too.

 

Burn or it could be getting infected...I'd check with a doctor if it's concerning you or getting worse.

 

More likely to get an infection from your own spit than from the slag. It was just red hot before it got stuck to your lip so all bacteria is dead. Try to keep it clean till it heals and wear the face mask while chipping that is what they are for. I wouldn't worry about toxic poisoning with the little bit that stuck to your lip, if you sat down with a shovel full of slag on your pizza maybe.

 

I'd agree it's probably a burn that is getting infected. This isn't something to fool around with. Infections take hold fast and can do some serious and permanent damage, especially with burns. That's why in the burn ward they are very careful to try and avoid infections, even going so far many time as to dedicate things like stethoscopes to individual patients so there's no chance one person will get something from another.

See your doc ASAP and if things seem to get worse or you have other strange symptoms, don't hesitate to go to the ER.


You might find some of these reads useful.

http://weldingweb.com/showthread.php?403121-Tough-safety-lesson-(graphic)

http://weldingweb.com/showthread.php?248971-Well-crap-burn-turned-bad