i doubt its serious(yet)it is probably a clogged oil gland or something like a pimple.try holding a hot washcloth on it several times a day til it drains.maybe its more serious(being next to your anus)because the bacteria there is NOT tolerated by the vagina(or any other tissue for that matter),so cross contamination by your hands could occur in your vagina,or bacteria could enter via broken skin,or squeezing the bump could cause the pus to back up into the tissue and spread infection,possibly causing huge problems,like an abcess or something.