Thanks for posting your query.
According to your description , pain and swelling over your lump seems to be inflammatory in nature.
I advice you to give you rest to the part affected, take anti-inflammatory drug like motrin
1 tablet with food as and when required (upto 4 tablets daily) to reduce pain and inflammation and consult your doctor for thorough examination of ankle and rule out any infective cause.
Wishing you good health...
Dr Saurabh Gupta.