I dont want to forget about him, but i know i have to. What do I do?
If you don't want to forget about him, then just see him as a friend. But, if you really need to forget about him... try to erase everything that mentions about him so it would be a less bother to you.
Occupy yourself with something else and just move on. Thinking about not thinking about someone is still thinking about them.
Live and Learn
Try to distract yourself with someone/something else but then again you can force feelings away