Noticed A Dark Spot Of What Appears To Be Pooled

Noticed a dark spot of what appears to be pooled blood behind my right knee, right at the joint. Also have a pain from right buttock down my leg, which could be sciatica, since I have suffered from that in the past. I have some knee pain as well. I have not had any injuries, but did fly a few days ago, and flying again tomorrow. What could this be, should I be concerned?