AS others have pointed out, there are a million things that can set a CEL, ranging from the sublime to the outrageous, sometimes affecting drivability, and sometimes not. No answers to your questions are possible without knowing what error codes were set in the computer.
Sometimes a CEL will be set by a spurious sensor reading. Usually when that happens, they go away after the 3rd or 4th restart. Then there are serious ones that require the repairing mechanic to reset the light after the fix is applied. Again, nobody here can have a clue without knowing the error codes.
Sometimes there are problems that arise that lead folks to drive for years without a fix. And sometimes the vehicle shuts down and becomes a brick until the issue is resolved.