Why a bubble forms
A wallcovering needs a sound, dry and properly prepared surface. A pocket of air or a local adhesive issue can create a bubble soon after fitting. A bubble that appears later may point to a change in the wall or room, including dampness.
The timing is the first clue. A single spot immediately after installation is different from several bubbles appearing after rain or beside a bathroom.
How to check it safely
Take one wide photograph showing the wall and one close photograph of the bubble. Record when it first appeared and whether it is growing. Check for staining, a musty smell, cool damp patches or peeling paint.
Do not puncture it or inject adhesive yourself. Some wallcoverings have delicate surfaces, and opening the face can make a professional repair harder. If there is moisture, find and fix its source before treating the finish.
Can it be repaired?
A small bubble on a dry, sound wall may be repairable by the installer. Widespread or recurring bubbles need the wall preparation and adhesion checked first. If the substrate is damp, a building or plumbing professional may need to investigate before the wallcovering can be repaired or replaced.
Bring the product name, installation date and photographs when asking for help. Those details let the installer decide whether a local repair is sensible rather than guessing from the pattern alone.