Hi thanks for your question.
You have developed lump on your leg following trauma, the lump is associated with bruise
from ankle to knee.
You have not mentioned in your question, whether your GP advised you,-Ray of leg, and if so what is report.
Has he ruled out any green stick fracture
(small hair line fracture, the bone remain in place)?
The lump you’re mentioning could be hematoma
(collection of blood under skin) and it will disappear in due course of time.
Pain could be due to injuries to the soft tissues or it could be due to green stick fracture and should respond to analgesic
Since you are patient of rheumatoid arthritis
, in which immunity is reduced due to various drugs.
So hematoma will time to regress in you.
You have to take due care hematoma should not get infected.
If symptoms remain persistent, for than 2 weeks, consultation with orthopedician is encouraged.
Hope I answered your question.