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It is likely to be fluid / pus imparts a white colour; blood gives bluish discolouration...
You have not stated your age, gender, personal habits, family history or co-morbidities
Never middle with it.
See an Orthopaedician / get examined / get investigated, if necessary...
Rest to the part (Splinting if necessary & avoiding weight bearing) is important
Non Steroidal Anti Inflammatory Drugs like ibuprofen
reduce pain & inflammation
compress in first days / later warm compress - help
Wishing speedy recovery