A phone flashlight held against your skin is a very low intensity, ordinary light source. It does not penetrate deeply enough to reach or affect your baby at 22 weeks, and an occasional check like this is not known to cause any harm.
Next Steps
There is no real benefit to repeating this often, so there is no need to make it a daily habit. Keep tracking your baby's wellbeing the usual way, by noticing how often and how strongly you feel movements through the day.
Health Tips
If you ever notice a clear drop in your baby's usual movement pattern, do not rely on a flashlight check. Please see your obstetrician the same day, and feel free to mention this habit at your next visit too.