I have just a large red lump on my leg, hard to the touch and very itchy, and very large. Swollen and red. Should I be alarmed?

Have it seen. It is difficult to diagnose issues with the skin without having them seen by a physician. As a "very large, swollen, red lump" is not normal on the leg it would be a good idea to have a physician look at it. The fact that the area itches would make me suspicious of possibly it starting out as an insect bite; however, a secondary infection requiring antibiotics is certainly possible.