That depends on the pus on the inside of the foot. It isn't always a hard lump. My first case had cottage cheese like pus, & sticky fluid. Had to cut into the foot to clear it all.Bumblefoot surgery isn't really "surgery" most of the time. You soak the feet to make the scabs soft, about fifteen minutes in Epsom salts, and then scrape the scabs off with your thumbnail. Most of the time, the pus plug comes out attached to the scab as it's removed.
Then wash well with soap and water, dry, and pack the wounds with antibacterial ointment, and bandage to keep out dirt. Check in two days, and repeat if it's not healing.