It's funny that last week I also had a flu and a neck pain from awkward sleeping position. It took me couple days to recover. How, you ask?
Easy steps:
1. drink plenty of warm clean water and
2. drink plenty of herbal tea (non-caffeine) with lemon + honey
3. daily short walk around the house
4. eat small meals - chicken soup and boiled veggies
5. light warm-up exercises instead of intense workouts during the day
6. light exercises before bedtime <---- this helps me sleep better without neck injury.
My patreon (female artist) also suffered from a flu. She also recovered as well as I do.