What can I do I stepped on gl?

Um.. My mates and I.. Because it was a hot day decided to play water fight. I ran across the street bare footed. And I stepped on gl. There was blood.. And that was yesterday.. Now the area on my foot has a black ring around it.and is quite swollen. I don't know what to do.. I don't know if it's still in there and it's near impossible to walk on, and is quite painfull.. I need Help!!