Try using moist heat like a warm face cloth, or a heating pad before you massage. It can help loosen the contents of the duct.
I'd get it looked at if it doesn't clear on its own in the next few days, but at the first sign of feeling flu-like symptoms (body aches, pains, fever, chills, malaise, fatigue) get seen asap! That indicates mastitis and if feels like running into a brick wall.