Why am I starting to see bubbles after painting a wall?
If it's concrete or plaster applied to brick, that's a porous surface, which can lead to bubbles like this if not sealed/primed beforehand. At this stage, you could treat the paint itself as your (rather expensive) primer coat. Basically the wall has now been sealed with paint instead of primer, so you can sand it smooth and paint a final coat on top. As long as you don't fall prey to the other things that can cause bubbles (all user error, not product issues) then you should have a smooth finish.

Those you asked are likely correct that this is nothing more than a cosmetic issue. Other more serious concerns (excess moisture, etc.), would likely manifest in a more obvious way than just tiny bubbles in paint.