Sorry to (do something), but (sentence)
When you want to do something that you think might annoy people, but you need to do it anyway, you say "Sorry to ___". For example:
Sorry to say this, but I don't think that's a very good idea.
Sorry to leave early, but I have to go and pick my son up from school.
If you want to be more formal, you say:
I'm sorry to interrupt, but may I ask you something quickly?