The nerve is dead on my tooth?

i have this lump on my gum this little ball it hurts like hell mostly when i try to play with it i mean it must be because i used to not have a tooth in the location where it belonged the tooth with the dead nerve is in back of my vampire tooth and my vampire tooth is where the dead nerve tooth is supposed to be my mouth is preetty messed up man and now i have braces fixing the problem and i brushed earlyer and man my mouth hurts like hell i always had the lump for about 2yrs it gives this foul stench when ever i blow air out of it what can i do to get this resolved?