Myself 31, having mild pain in groin,nearby nearyby penis from.past week and no other symptom, no bulge, no fever, no unsafe sex. what can be the reason?

Groin pain: A pulled muscle may be most likely. Maybe hernia? If tenderness or swelling, perhaps a minor infection/inflammation anywhere in the leg or foot on that side. You say no unsafe sex, but you listed "unsafe sex" as a topic tag. However, no STD is a likely cause, even if at risk. But get tested for STDs if in doubt. Doesn't sound serious, but if it continues and you remain concerned, see a doctor.