Thanks for posting your query.
This small swelling could be a haematoma( collection of blood) due to rupture of minute blood vessels as a result of injury
over that area or a lymph
node in groin region which might get enlarged due to infection in nearby area.
I suggest you to consult an orthopaedician nearby for a detailed examination of swelling, investigation and traeatment plan according to that.
Wishing you good health
Dr Saurabh Gupta