Please don't worry. Taking finasteride for only 6 days is unlikely to cause any change in testicular size. Testicles can naturally appear slightly bigger or smaller depending on temperature and muscle contraction. This alone does not suggest testicular cancer.
Since a surgeon has already examined you and found nothing concerning, that is reassuring. If you can feel a persistent lump, swelling, hardness or pain, please consult a urologist and get a scrotal ultrasound for confirmation.
Next Steps
Avoid repeatedly checking your testicles, as this can increase anxiety. If you notice any persistent change, consult immediately
Health Tips
Please don't rely on Google/AI searches to diagnose yourself. Most testicular swellings are due to non-cancerous causes. Stay calm and get examined if the change persists.