Since I work outdoors around horses I get bruises all the time. Kneeling on a hard floor, walking into a fence, getting kicked by a cranky pony, you name it. A bruise is not a sign of Lupus...it's , well, a bruise. Put some ice on it if it's really bothering you but that and time are all it needs.
Btw, My cousin has Lupus so I am familiar with the symptoms, (nothing like yours), and even then hers is well managed with medication.