But when it comes to the grammar of saying sorry, what rules apply?
Sorry is hard enough to say, or write, without letting it get buried in undergrowth.
Therefore, sorry has to stand alone. No prepositions. No prefixes or suffixes.
Sorry, but …
Sorry – you must understand …
Sorry, OK, so it may have been my fault …
Sorry – yes, all right, you win, again …
On its own.