Hi! ive had a bruise on my arm for a couple weeks, maybe half an inch, and there is an equally large knot under it. it also is still pretty black, though the edges are slightly yellow. i dont remember getting it. do i need to be seen for this?

Being seen will give you a more definitive answer, but without seeing it, this sounds normal for a bad bruise. The yellow edges happen as the bruise is healing.The lump underneath is from a collection of blood under the skin, caused by the same trauma as what you are seeing on the surface. If it’s not enlarging and you’re not having more bruising or bleeding in other places, you can probably wait.