Hi,
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