What should you do? Well the above posters are right on the money...so the ONLY thing you can TRY (cause there is no guarantee it will work) is to apologize to your bf, tell him you were only trying to help / be the peace maker but going forward you will abide by his wishes, since he IS the father, and will referr any questions such as those you tried to field, back to your bf.

I would also add to the bf, that it is because you don't have kids of your own, that while you only mean well, you do stumble sometimes and would appreciate if he can help you understand a few things regarding the rearing of a 15 year old, which is tough for anyone. AND, you are AWARE you have no kids, so being reminded of it in the manner your being reminded (snide comments?) is not helpful.

Say all of this in a non-threatening sit down with your bf...do NOT go on the defensive if he decides to be pouty. Will it feel like you're being a suplicant? Probably....but you stepped out of line. So suck it up, and apologize, and then set the boundries that should have been set between you and your bf's son...preferably, with the bf's input. In FRONT of the son. So everyone is on the same page.

Take care...