I Have A Bruise On My Upper Leg. I Don't

I have a bruise on my upper leg. I don't ever remember hitting it and it's the size of a softball. It's gotten noticeably worse in a matter of a few day. There is a huge dark purple line going through it. Like a vein. I've had the dark line (vein like) before but never a bruise this big around it. I'm worried it could be a blood clot. Should I be seen ?