I woke up this morning with an engorged breast which is sore, painful and lumpy. My baby nursed and the lumps and pain still did not go away. I pumped out the rest of the milk and still have this painful feeling in my breast. I have never experienced this before and I've been breast-feeding for five months now. Is this a plugged duct? And what can I do about this .. it's really painful. :(

UPDATE: 

Thank you all for your advice!! I ended up using warm compress and nursing and pumping and thankfully it went away later that day! I'm so happy it wasn't too bad .. I've bought the Lansinoh gel pads just in case it happens again.