http://tinypic.com/r/dos7ix/9

Hello,
I recently pugged my Alphonso mango tree and a few days after I noticed the spot where I made the cut was darkened. It continued to worsen and today it is as seen in the pic. The very tip is black with spots of white that look like white ash you'd see from a fire. Does anyone know what I'm dealing with here? Thanks so much for any help!
Nico

also, when I made the initial cut the center of the wood looked clean and healthy, no dark center or spots of any kind.