Hello doctor, 2 days ago I notice a little mass inguinal under my skin on the right leg! It's a little painful on touch should I be worried about it?

Probably not. Lymph nodes in the groin commonly enlarge and get a bit tender when fighting off germs entering the skin through cracks in the feet, etc. If pain gets severe, or the lump gets much larger than a marble, or doesn't improve within 2-3 weeks, then an exam is warranted to look for infection or other problems.