Please help! pain on my left leg and also a lump of something. could you explain the cause of this?

Can U Be specific ?: Where in the leg is the lump? Leg is between the knee and ankle joints. It could be anything, arising from skin, fat, muscle or the bone. If its near a joint then it could be from joint tissues. If there is any injury to it, then it could be a collection of blood or fluid, which will improve over 2 weeks time, otherwise you need to see a doctor to have it checked.