The lump seems to be part of the engorged breast. The only way to get your breasts to produce more milk is to empty each breast FULLY at the time of breastfeeding, making sure it gets empty at each feed.
If it gets super hard, he may have a tough time latching on. At such times, squeeze a little milk out to soften them, making it easier to latch. Offer him a feed multiple times if he doesn't latch or feed well.
DO NOT get into the vicious cycle of baby not feeding well, your breasts getting engorged and then slowly milk supply diminishing.
Wish u the best!