I got small lump top of my hand almost month and its hurt when I press it?

There are any number of things this could be...reaction to a foreign body (i.e., splinter), a bug bite, a cyst (fluid filled sac), etc. Show this to an adult. Stop pressing on it. If a black area of the skin appears you should see a doctor. If it becomes red and a hole appears in the skin, see a doctor. If it enlarges, becomes painful when not pressed, or interferes with activities of daily living, see a doct.