How do you say sorry i did no know you speak spanish in spanish?

A bit difficult to translate because ambiguous. It could be:

(I'm) sorry (that) you speak Spanish = Lo siento que hables espan~ol

Though more likely is:

'Sorry! You speak Spanish (and I don't)' =

'Lo siento! Usted habla espan~ol (y yo no)' Pronounced:

'law see-ENTaw! oosTAY AHBlah esspannYOL (eeyaw naw)'