Boil drains, should you pour peroxide on it and cover it?

Rupture. When a boil ruptures, generally drainage of pus-like discharge will ensue. It's best to keep the affected area covered while the boil heals on its on. There is nothing otherwise that needs to be done than to keep the affected area clean, dry and dressed. It can take 1-2 weeks to completely heal, dependent on the size of the boil.