Use 'queasiness' to describe a gentle feeling of sickness, less intense than outright pain. After eating too much candy, she complained of queasiness.
Pro Tip 2/3
Not Always Illness
'Queasiness' can result from anxiety or stress, not just stomach problems or illness. Before the interview, his queasiness wasn't from being sick, but from nerves.
Pro Tip 3/3
Temporary State
Queasiness usually refers to a temporary and not a chronic feeling of sickness. The queasiness passed quickly once she got some fresh air.