Welcome to the forum.
From description ,it seems you might developed soft tissue injury
. this knot most probably formed due to haematoma
formation (collection of blood) which might get fibrosed or calcified.
I suggest you to consult an orthopaedician nearby for a detailed examination of swelling. You may get the X-ray of the area affected under his/her guidance.
Meanwhile give hot fomatation over it, You can take Tablet Motrin
1 tablet with food as and when required (upto 4 tablets daily).
I hope this information has been both informative and helpful for you