in :h NERDTree:
:NERDTreeFind :NERDTreeFind Find the current file in the tree. If no tree exists for the current tab, or the file is not under the current root, then initialize a new tree where the root is the directory of the current file.
I don't think it's bound to anything by default, so you have to do a keybind yourself.
nmap ,n :NERDTreeFind<CR>
is what appears in my .vimrc, along with
nmap ,m :NERDTreeToggle<CR>