Jump in the hot shower and rub the crap out of the lump. Heat packs are also helpful.
Not meaning to contradict, but massage of a lump should be very gentle, fingertip light touches only, or else you run the risk of damaging the duct and causing further problems. Heat is good before you feed from that side, but an ice pack and anti-inflammatory afterwards helps alleviate both the pain and inflammation causing the blockage.