Gaining weight back after surgery

A month ago I had a partial glossectomy (removal of part of the tongue)after being diagnosed with oral cancer.
Recovery is going as expected; it's slow and painful but I'm getting there.
For the first 3 weeks I was on a liquid diet. I've always needed to eat around 2400 calories just to maintain my weight and it was harder than I thought to get those calories in liquid form, plus I've read that more calories are needed for recovery. .
Long story short : I've lost 6 kg I could not afford to lose,plus muscle mass.
I'm gradually eating more solid food and trying to include nutritious high calorie foods. I'm pre-diabetic so can't really have things like ice cream etc so it's not easy.
My question is this : to regain the weight,can I do this by sticking to my usual maintenance calories or do I need to eat more on top of that ? I've also given up alcohol (given that it could well have been a cause) and so that means I'm already on fewer calories than when I was drinking a couple of glasses of wine.
Thanks for reading this.