I am a 26 year old female. i had pain behind my knee yesterday. after standing for a long time. today there is a large bruise. a cause for concern?

Posterior location..: 26 y/o says I had pain behind my knee yesterday. After standing for a long time. Today there is a large bruise. A cause for concern? Due to the posterior location of the bruise it should be examined by a PCP. It is most likely benign but; trauma, insect bite, phlebitis and other conditions that could happen in that location should be evaluated and managed appropriately.