It’s most probably a blocked duct. The best way to deal with it is to get the milk out. Pumping helps to some extent but I’ve found that my baby’s latch is the strongest and most effective. While baby’s sucking, I also massage over the lump. So far every single lump has disappeared with that method. I wouldn’t suggest hot compress because that just produces more milk and doesn’t solve the blocked duct, so the pain may get worse.
Keep latching! I've had lumps bigger than that, nothing works better than latching - cleated the next day
I think you're right. You can do hot compress and massage, hot shower and latch more often/pump.
Latch to deblister that