Breast lump, exclusive pumping?

I had mastitis last week. I’ve finished the course of antibiotics and the pain and redness is completely gone. However, since then, I’ve had a rather large lump in the breast. I’ve tried massaging before, during, and after pumping; increased fluid intake; and I’m taking sunflower lecithin. I can’t get this lump to work itself out, and I’m barely getting any milk on that side.

Anyone know what could help?