Contrary to popular belief, chiggers do NOT burrow into your skin. So coating the bites with nail polish accomplishes nothing.
The nymph form find a spot on your body with some restrictive clothing and then settle down for some fine dining. They inject a digestive enzyme that literally liquifies your skin cells and lymph, so they can suck them up. You don't feel the bite for quite a few hours and the itching begins a day or so later. REALLY big time itching.
Calamine lotion or other prescription anti-itch medications relieve some of the itching for a short while. And the itching seems worse at night.