Thanks for your query.Based on the facts that you have posted it appears that you have either a Staphylococcal infection
of the hair follicle or Sebaceous cyst
over the shaft of the Penis.
However final diagnosis can be confirmed only on clinical examination.
Please consult qualified Urologist
for clinical examination to confirm the diagnosis.
Take some antibiotics like Doxycycline twice daily for a week.
If problem persists even after taking antibiotics you may need to get it excised under local anaesthesia.