Hi Sarah,
I'd like to add more to Julia's answer.
1. "Like I said" - in a casual context
--> わたしが言ったように
2. "I hope you don't mind" - in a polite context, like "I hope you don't mind, but I need to be leaving now"
--> 気になさらないとよいのですが is one of the common translations but we have to change the way to say it depending on the context, besides there are various translations. In my opinion, "I hope you don't mind, but I need to be leaving now" is わたしはここをでなければなりませんが、かまいませんか / よろしいでしょうか?.
3. "Don't mind me" - in a polite context, like "Don't mind me, I'm just looking around"
--> 見ているだけなのでおかまいなく or more polite: 拝見(はいけん)しているだけですので、どうぞおかまいなく。
4. "Woops" - in a polite and casual context, like "oops" or "woopsie" like when you've made a mistake or accidentally knocked something
--> まあ / あら / あらあら, etc (used by women), おっと / あっ / ああ / うわあ, etc (can be used generally)
I think one of the polite expressions for this is すみません like 「あ、すみません。まちがえました」
Casual ones are
あっ、まちがえちゃった and you can also use other words I wrote instead of 「あっ」.
I hope this was helpful and my English isn't very bad.