Seek evaluation. Without knowing more, this is difficult to assess. By itself it may not be anything, it could however be an early yeast infection ( typically an odor, drainage and itchy) or an obstructed bartholin cyst ( unilateral), vaginosis ( discomfort, redness), simple overgrowth, hernia, etc. Treatment will depend on identify g the cause.
Infection/trauma... Infection of the area or trauma could cause what you describe. It should hurt at least a bit though. It could also be an allergic reaction to something.