Hi and welcome to HCM
From description it seems to be soft tissue injury
. Large lump might be due to haematoma
formation(collection of blood).
You need an x-ray to rule out any bony injury.
I suggest you to consult an orthopaedician nearby for a detailed examination. You may get the X-ray of the area affected under his/her guidance.
Avoid sitting for long hours. Do a cold
compress on the area of injury.
The pain and swelling might take over a week to subside.
I do hope that you have found something helpful and informative and I will be glad to answer any further query.