Hello, thanks for using health care magic.
It is possible that you have an affection of your left bartholin gland which could either be a cyst
or an abscess. Cyst develop when the drainage
of the gland becomes blocked and as such fluid accumulates causing pain where as bartholin gland abscess
results from an infection of the gland which is not necessary through a sexually transmitted pathogen. Cyst could require just warm compresses and pain relievers while an abscess requires antibiotics and might required open drainage (marsupialization) if considerable in size. It is less probable that the cause is the shaving because apparently its on the same day that you shaved that you noticed lump.
However, an appropriate diagnosis could only be made after a physical evaluation and as such, you should consult your doctor to rule out other possible diagnosis.
Dr. Achuo A. M.