At school we have a thing called a jumper made of wood the tallest one i hit my leg and have a lump that when i touch it lightly it hurts badly!!!!!!!

Painful lump: You may have a bone bruis in conjunction with a hematoma.If pain persists get an x-ray to rule out a non-displaced fracture

It depends on where: on your leg it hurts. If it is the shin you could have bruised the periosteum or covering of the bone which is very tender and may take a while to resolve.

Contusion: LIkely a contusion. I realize it may hurt, but this does not mean it is serious. Rest, ice, elevate and try some Ibuprofen for starters. If this problem remains very tender after a day or two get checked.