Clogged duct? (no picture)

Alex
Talk to me about clogged milk ducts. I think I might have one and I'm feeling uneasy about it. I have a red patch of skin next to my nipple and its tender. Also after nursing I can feel a lump on the inside. I've done a warm compress, dangle feeding and frequent emptying. How have you dealt with it and when does it warrant a call to the doctor? Thanks ladies!