Trim the window, then tile the wall.

What if I’m wanting to keep the tile the way it is? I didn’t plan on running tile the length of the wall, just on the bath surround.

This is a better picture of the situation.

I would get more tile, and finish that wall to the corner, so it looks like it was planned instead of running out of tile. Once thats done, cut a thin strip off the end of a board, the thickness from the window frame and the tile, so you get the window frame level with the tile, and then put your trim on the window.

Trim is normally nailed through the gypsum board to the wood framing and to the window frame. It appears you will have ceramic tile between the trim and the wood framing.

I suggest your remove the tiles where the trim would be, install the trim, then tile to the trim.

What type of waterproofing membrane did you use behind the tile?

I believe your window's jamb doesn't extend inside to be flush with the sheet rock. What's up with that? You'll need to build out the jamb before trimming out the window first. Then you need to remove a row of tile around the window and then trim the window. Once the window is trimmed you'll need to redo the tile you took out and cut to fit next to the trim. Don't worry, everyone makes a few mistakes and a learning process. An old timer once told me the difference between a tradesman and a good tradesman is the good one knows how to fix their mistakes. Take out the tile even if it can't be saved and buy new but first fix the window jamb.