Thanks for posting your query.
It seems you might developed bursitis
over knee due to constant friction over it.
I suggest you to consult an orthopaedician nearby for a detailed examination, proper diagnosis and treatment plan according to that.
Meanwhile give rest to your knee , you can take anti-inflammatory drug like motrin
1 tablet with food as and when required (upto 4 tablets daily) to reduce pain and inflammation.
Wishing you good health
Dr Saurabh Gupta