“我刚才说错了” 可以用 "I made a mistake" 或 "I misspoke" 表示。
"I made a mistake" 是一种正式的表达方式，指的是在说话或做事的过程中犯了错误。
例句："I made a mistake when I said that the meeting was on Thursday instead of Wednesday."
"I misspoke" 是一种更委婉的表达方式，也可以用来表示说错话。
例句："I misspoke when I told you that I had graduated from Harvard, I actually graduated from Yale."
来源：这两种表达方式均为英语固有的说法，广泛使用。