On Saturday night a really sore lump appeared right on that little bit of my back I can't reach. Felt like a really sore spot, but since then has got bigger and more painful. I can't lie on my back, and anything touching it is agony. It's red and sore all the time and is enormous (relatively speaking of course).
My DD has had a look at it and says there's no head on it so it can't be squeezed.
I'm tempted to go to the minor injuries unit at the local hospital but don't want to waste their time if it is just a spot.
I took a pic of it last night in the bathroom mirror and it's so bloody big that it's got its own shadow! 
Any advice?