So now what? That was long ago. Forum pvssyr suggests the next step is to aggro, defend from, and annihilate the BOS. No joy. Aggroed them twice with no visible effect, reloaded.
Did I miss a mission?
You are pretty much done with the Minutemen. You can either make the Brotherhood enemies or ignore them. To make them enemies just go aboard the Prydwen and kill Maxson and whoever else has decent loot. If you just kill some named Brotherhood member and leave, then you can't get any loot from the mission that wipes out the Brotherhood.