What do you do for black tongue?

i heard eat pineApples but im going through the same thing right now.i just got my tongue pierced about 2 weeks ago and my tongue was looking weird and i went to the er.he said my tongue looked fine and gave me penicillin to take 4 times a day and one of the side affects was black tongue.im not gonna lie i didint want to take it.been taking it for about 4 days now and my tongue is starting to look wierd.ive been brushing my tongue like crazy.its not black but its like white looks weird.i need help too.some one help us:( ty