How To Treat Discoloration And Pus Formation Under The Thumb Nail?

On my left hand I have a discoloration under the nail of my thumb. This started about eight days ago with just a slight deeping of the nail face. Within a few days a tunneling effect all the way back to the base of the nail bed. I had no pain but noticed that if pressed from back of nail bed towards the front I could expell puss from the tunneling area. I have soaked the thumb in Epsom salt for a couple hours for two hours or more over the last few days. I just soaked it in hydrogen peroxide and it bubbled a lot but still no pain. This infection is deep and I have no idea how it started, any thoughts?