With a large finger nail file, file down the top surface of the nail, from the tip, back to the cuticle, where it makes the sharp bend down into the flesh - the 'spine' I call it. File it down until the curvature of the nail seems uniform from side to side. This takes a fair amount of time and elbow grease. This will make the nail much more flexible and not so prone to be driven into the flesh by the pressure of standing, walking, etc.
I had ingrowns on both big toes for 18 months. 36 hours after doing this, all discomfort was gone, and six months later, they're just fine and I've not had to file them down since.