Hello and welcome to HCM,
I read your query and understood your concern. It could be either sebaceous cyst or like you mentioned,
Herpes.
Herpes though is more painful , and would rarely present as a 'big' lump. Since it is recurring and even after
drainage of clear fluid its not spreading, it doesnt sound like herpes.
Other being sebaceous cyst, maybe due to damage to hair follicle, or maybe infected ingrown hair. In both the cases take an antibiotic like
cephalexin, get full course prescribed by your physician. Put warm compresses over lesion for 2-3 mins, 4-5 times per day. take anti inflammatory like
paracetamol, and anti-itch like cetrizine/
loratadine.
Also dont scratch, squeeze or puncture the lump as it may cause recurrence of infection.
Hope I helped