The top of my foot is swollen and bruised with a lump could it be broken?

Possible: More ifo would help, like was any trauma involved? A lump on the foot could be a ganglion and many things. See podiatrist.

Possible: Clearly, an x-ray would help detemine whether you have a fracture. However, a hairline (stress) fracture may not be evident on x-ray until 10- 14 days post injured. The lump may be swelling or a hematoma as a result of the injury.