Thanks for posting your query.
From description , this large bump over your leg most probably formed due to haematoma
formation which might get fibrosed or calcified.
It will take few weeks to months to get disappear.Apply hot fomatation over it, You can take Tablet Motrin
1 tablet with food as and when required (upto 4 tablets daily).
If there is any redness
, increased temperature and tenderness over swelling, consult your doctor to rule out infection.
Wishing you good health
Dr Saurbh Gupta