while it may be possible, its frowned upon. The docker way is immutable containers, so you want to edit the nginx config you 'cant' just do it in place, you need to make a new container with the new config and a new process and kill all the existing containers(and hence processes/connections).

docker is basically at the point today where mapreduce was a few years ago. while it may solve some problems, its not a thing that solves everything.