disasterboard

Thanks very much for your input, appreciated. I guess I was worried about a leak, and also read that grout is water-resistant but not strictly waterproof.

Howdy all, Fairly new to DIY, and live in a flat. I recently tried to remove some of the grout between my shower/bath tiles with an oscillating multi-tool because mould was appearing, even after we tried to remove it. The tool worked well - a little too well. Whilst I was happily working away, I went too deep. I now realise I've taken a few mm out of the plasterboard behind the grout along most of the tiles in the shower/bathtub area. I've been told that bathrooms have special water resistant plasterboard. Now I'm worried that I've left it even more vulnerable to mould and damp, if there is some kind of waterproof lining for bathroom plasterboard. Should I just go ahead and re-grout? Or is there something I can put behind the grout to improve the situation? Or do I need to do something more drastic? I would rather not have to re-do the plasterboard and tiles! Thanks all!