Newly plastered inside of basement wall - sounds hollow

[Emma841]

We have plastered an old basement wall inside the laundry room, laid a pretty thick layer to get it straight and nice. Now it sounds hollow when you knock on it
Can we tile on it anyway?
Or can we attach those round plastic plugs available for plastered exterior wall systems, or does everything need to be redone with plaster mesh, etc.?

Thanks

 

[Centano]

Does it sound hollow everywhere or just in certain places?