Sudden sensitivity can come from several different problems
A tooth that suddenly becomes sensitive may be reacting to a new cavity, a cracked edge, a worn filling, gum recession, grinding, or exposed root surfaces. Sensitivity is a symptom, not a diagnosis.
That is why home remedies can miss the real problem when the change is new or getting worse.
The pattern of sensitivity matters
Pain to cold that goes away quickly may mean something different than sensitivity that lingers for a long time or pain that only happens when you bite. The more specific you can be about the pattern, the easier it is for a dentist to narrow down the cause.
When to schedule an exam
If the sensitivity is new, stronger than usual, or tied to one particular tooth, it is worth scheduling an evaluation. Catching the cause early may help you avoid a bigger restorative problem later.