*UPDATE*
Well it turns out...
The day after the 'lump' appeared on my nipple, I had been in a 'hot tub' with a few mates getting beer'd up
My mate Justin, That also used to have his nipple pierced.. ALSO had the same symptoms
Same lump, Same side of his piercing, Same pains and its now gone.. the same as mine..
So we're thinking it was something in the water thats affected us, Even though the water was from the Kitchen, We used a hose to fill it up from the Kitchen sink
Odd.. But either way, Its gone now...