How Should A Shoulder Weeping Patch With Reddening And Pain Be Treated?

I've just noticed a weeping patch on the top of my shoulder. Its seeping through my shirt. There is a very slight redening of the skin and it stings a little. I've already had a papiloma removed about 6 years ago which started with similar symptoms, but there is no visable mole to start with this time. Should i see a GP or wait to see if it gets worse?