I Recently Bumped My Arm While Moving Boxes. I Have

I recently bumped my arm while moving boxes. I have a little bit larger than a half dollar sized bruise on my arm, which expanded, but it now healing from the bruise. It does have a kind of squishy lump that feels as though it's a cyst. I do have lupus, but know this is from an injury not illness. I have been light headed a few times over the past few days, but am under stress with a death in our family. Should I see a doctor?