Replacement window sitting below the brick line?

I installed this replacement window yesterday. After building out a new sill board, I tried to install the window and realized it wouldn’t fit. I had to remove the 1.5 inch thick sill board to put the window in, and now the new window just sits on the framing of the rough opening (it is just dry fit at the moment). However, the window is still very tight in the rough opening, and now the bottom of the window sits below the brick line.

My initial plan for the sill board would have covered the brick gap, but now that sill won’t fit. Do I just push the window out, as close to the brick as possible? Or do I need to cut out some drywall and raise the rough opening?