Hi.. Welcome to HEALTHCARE MAGIC.. As per your query painful lump over the shin after being hit by football is due to inflammation and hematoma formation.. Due to injury there is rupture to small blood vessels leading to spillage of blood into the soft tissues and along with it there is also release of inflammatory exudate,collection of inflammatory cells and accumulation of dead tissue in the area of injury, all of which leads to redness, swelling and rise in temperature in that area.. At times the hematoma gets encapsulated and localized and there is formation of a hard tender and firm lump.. No need to worry as it will resolve, althoug it can take from a few days to even months to resolve.. You should do alternate warm and cold compresses over the lump. Apply Thrombophob [heparin containing] gel. Take anti-inflammatory painkiller like Ibuprofen. Elevate the legs while laying down. You cal also apply numbing gel over the sore lump to reduce pain.. Hope this information helps.. Thanks and regards.. Dr.Honey Nandwani Arora.