Thanks for writing to us.
The large lump is likely to be due to a hematoma
formation in the area.
It seems to be soft tissue injury
. You need an x-ray to rule out any bony injury.
You need to avoid massaging the area and take a mild pain killer for relief. In case there is an acute pain and a sudden increase in swelling then consult your physician for a direct examination to rule out any infection in the area.
I do hope that you have found something helpful and I will be glad to answer any further query