Scared of Anal (tmi)

So a few years ago my hubby and I were doing the deed (PIV). I was face down and he was going hard and fast. He accidentally slipped into my ass for a few thrusts. He’s very large and it was excruciatingly painful. I started yelling and crying and he felt terrible for hurting me. But ever since then he’s been fascinated by anal and said he wants to try it for real more than anything. I was pretty traumatized by that experience and have never had any interest in it even before that. The thought of him playing with my butthole grosses me tf out. Anyone have any tips or advice on how to move on from the trauma and trying anal in a safe and way less painful manner?