Suggest Treatment For Cyst Like Mass In Upper Back

My husband has a large cyst like mass on his upper back , actually r shoulder I guess. It had started to drain a couple of days ago, I examined it and with even light touch large amounts of pus like substance came out, now 2 days later, still red, sore, smaller and still w pus on pressure. I used a sterile needle and opened it up a bit and drained out a pretty large amount of malodorous yellowish puslike material, again today....smaller, remains swollen and hard to touch.