Hi . That might be a blood clot, or deep vein thrombosis, which does sometime happen to people with PsA. I would get it checked out immediately. Most likely, it will eventually burst and you will be bruised, but fine, but it can also dislodge and travel through the vein. That would not be good. Keep be posted if you feel comfortable doing so. I will be thinking of you. - Lori (Team Member)