Painting - Painting on a cinder block interior wall

I am painting a mural at my kids school, the wall is cinder block and was yellow. I wanted to start with a white background so I painted an area with a premium interior flat paint, it started out fine but when I was almost done when I rolled over an area I already painted the paint came up. Do I need to go over it with a primer? Can I do that now? I asked what type of paint was on the wall ( a little late and they thought it was a water base latex) Any help would be great. Thanks, J

Welcome to the forums!

You probably should have used a primer but it won't do much good now unless you strip off most of the paint you applied :eek: :wall:

If the previous paint was a latex enamel, your flat will probably adhere ok. If it was an epoxy or an oil base enamel, you may have trouble later. At this point I'd let it dry for a few days, sand and touch up as needed...... and hope/pray for the best :D