Trying to translate your initial phrase directly may be too burdensome, but beginning a request with "If I may...," has a direct translation suitable for you:
よろしければ。。。
Here is an example, though the whole sentence is probably a bit too stiff for your purposes:
If I may, I'd like to ask you a few questions about something else.
よろしければ別のことをいくつかお尋ねしたいのですが。
Source: I searched "If I may ask" on http://eow.alc.co.jp
Please do the same if you would like to see other examples.
If you would like this response tailored to a specific quote, please provide one.
Among friends, one could say,
ちょっと聞いてもいい?。。。