Good news, Louisa!
Wrinkly, don't worry about whinging, everyone deserves one now and then! I wonder if your pain meds might be having an impact either on metabolism or on water retention? Either way, if you continue to stick with the diet you will still be burning fat (if you're in ketosis) and the protein will be helping you to develop muscle, so you are still on your way to your goal of being leaner and fitter, no matter what the scales say.
I weigh myself first thing in the morning but my weight can vary by as much as +3lbs at other times of the day. Your body does go through natural fluctuations, if you're sticking to the diet then I very much doubt your 1lb is going to be new fat deposits.
I know it's still disheartening though. Chin up, hun.
x