The red patches and painful blisters may be a reaction to Tinidazole, especially since the symptoms started after taking the medicine. Drug-related skin reactions can sometimes affect sensitive areas like the mouth or genitals and may continue for a few days even after stopping the medicine. Pain during urination can happen when the skin around the area becomes inflamed or develops sores. Keep the affected area clean and dry, and avoid using harsh soaps, antiseptics, or scented products. Wearing loose cotton underwear and drinking enough water may help reduce irritation during urination. Do not burst the blisters or apply random creams without medical advice, as some products can worsen the reaction. A dermatologist or physician should examine the rash soon, as genital blisters following a medication reaction may require specific treatment and close monitoring. Please seek urgent care if you develop fever, mouth ulcers, eye redness, skin peeling, or rapidly spreading rashes.