Blocked duct?

C
So I have a lot more nipple pain on my left breast. My 10 day olds latch has gotten a lot better and neither nipple is red or bleeding anymore but my right breast seems to be doing just fine while my left is still struggling.
Last night I felt a small lump near my armpit and I notice that even after she feeds, my breast is still firm in the area of the lump. She also seems to be a little more fussy on that breast.
What should I do about this?