I have a painful pimple like bump with white head on my elbow. what could it be? could laying on my bed or applying pressure on my elbow at my desk cause it?

Might be infection o: The pimple & white head means you might have slight infection in your skin , if it is too painful or you are having fever , chills you might need a physician's visit . Otherwise if it is small i would not pop it , i would apply warm compresses which will expediate the healing. Really the size will decide if you need antibiotic / incision & drainage. Also its notb/c of pressure, its skin infection.

Yes: This could be as simple as a pimple that has not come to surface yet. Constant pressure or irritation to the area can cause this. If you are having fevers, chills or limited range of motion of your elbow joint, a more serious infection could be developing and you should seek medical attention. If not, a warm compress and avoiding the pressure to the area should be helpful.