What can I do about this?

Yesterday morning I discovered a bed bug bite on the back of my upper arm. Last night it swelled up to about 2 inches in diameter and my whole arm ached when I tried to do anything (including typing). My boyfriend and I concluded that the swelling was probably putting pressure on a tendon or pinching a nerve. Now in a couple hours I have to start packing boxes and the damn bite is almost 7 inches!!! I don't have benedryl and apparently the ice didn't help last night.