First off, I am sorry for your loss.
Second, I think your decision to keep the weapon is a very personal decision, and it's hard to give suggestions without more input from you. In short, I think any suggestion I would make would hinge on 2 questions: a) Does being around this gun remind you of happy memories, sad memories, or none of the above?; and b) Is this a gun that you want/need/can put to good use?
My grandfather shot himself, and eventually died from the wounds. I inherited his shotgun and a couple of pistols from my father, and wouldn't be surprised if one of them were the gun he had killed himself with. I never met him, as this happened about 3-4 years before I was born. I keep his shotgun in the closet for home defense. For me, I have no memories associated with the shotgun, and it serves a purpose, so I keep it. If, however, you see that gun and are pained by memories of a lost loved one, then I would reccomend selling the gun. There is no obligation to keep such a weapon, and no need to punish yourself with those kinds of feelings. Only you can make that call, and know that if you want to offer more details, we would be happy to read and reflect. You can also feel free to PM me if you don't feel comfortable posting details like that on an open forum.