I am painting a child’s room and painted part of a wall to see the color…however I didn’t prime it first. What do I do now? Do I have to use primer first?
Primer isn't always needed. If your new paint is the same type as the old then you don't need primer. Example- New paint is water based (acrylic) and old paint was the same then no primer needed.
If you don't know the type of old paint and the walls are very smooth and shiny then using a primer is a good idea. Better safe than sorry.