Clogged milk duct???

Hannah
I have a super sore lump in my breast that's was not there when I went to bed. I googled this and it says it could be a clogged milk duct. It is 4 am and I've got a heating pad on it and LO just fed so can't nurse, and I already pumped ( that's how I found it I thought I was just still engorged so that's why I went and pumped). Any other ideas? I will call my doc when it's not so early but wanted to see what yall do about this. And what the h ck causes it? I feed every 2-4 hrs on demand, don't wear underwire, but I did have a lot of stress last 3 days. Can that cause it? 
 FTM here and LO is 4 wks old. Exclusively breastfeeding.