Is it normal for him to eat so little? Should I choose certain foods over others? Should I be concerned?

Hi, last Thursday afternoon my boy (2 years old) caught/started a stomach bug until Friday night. Since Saturday, he keeps what he eats and drinks. The rhythm of life is back to normal! Monday morning he had diarrhea, but was fine. He had not had a bowel movement since his stomach bug and noted that while he was sick, he only had vomiting. However, he eats very little or hardly at all at mealtimes. As much the meals that he prefers and what he asks for, does not eat them and if not, in the middle of eating he pushes his food away, complains and says no. He drinks a little milk in the evening, less than usual so I give him less, but he takes it.