I have a lump on the top of my foot and it hurts and i don't know why?

A lump : Is not normal, nor is pain so it's a good reason to visit the foot doctor. You may have a ganglionic cyst which is a benign cyst filled with jelly like fluid but without seeing it you can have something else....Go to the doc for a check up.

See Podiatrist: Could be a number of things from a cyst or a spur or other problem. Have it checked out.

Ganglion : Get checked out. The lump needs to be evaluated. Ganglion's are common on the top of the foot..

Never normal: Unless you recall trauma, lumps are not to be ignored. See a podiatrist for evaluation.

Could be cyst: This could be a cyst as in ganglion or it could be a malformation of one of the bones in your foot resulting in an exostocis.