In the current scenario, I would ask you to see a specialist for a proper clinical assessment. The cut probably resulted during an intercourse and owing to constant movement, healing often becomes difficult even though the labia have very high vascularity. Zinc creams are often helpful in healing and it is essential that you give rest to the part until it heals. This means you should avoid intercourse until complete healing and also avoid using any tampons during menstruation
, but applying sanitary pads. Hope this helps.