Simple answer

Can you force yourself to forget someone? No.

You can make small steps each day, and try to move on. You can delete pictures, throw away keepsakes, and refuse to contact them ever again. But memory is persistent, and leaves when it so chooses, not when you want it to. The more energy you put into trying to forget, the more energy is put into ensuring that you won't. Relax your grip, release your need for control, and trust that these things will give way to the sands of time.