A burning sensation during urination with a small ulcer at the tip of the penis may be due to a urinary or sexually transmitted infection, such as Urethritis or Genital Herpes. Since Doxycycline helped reduce the burning, but the ulcer is still present, it is important to consult a doctor for proper examination and tests. The doctor may recommend specific antibiotics, antiviral medicines, or topical treatment depending on the cause. Avoid sexual activity until the condition is properly treated, and maintain good hygiene.

Swelling of the lips and rashes after taking Minocycline may be an allergic reaction, which can be serious. Stop the medicine immediately and contact your doctor or go to the nearest medical centre. Antihistamines or corticosteroids may be needed to control the reaction. Avoid taking this antibiotic again, and always inform your doctor about this allergy in the future.