Susie and Chuckles: Thank you for the feed back. Me too I had no idea how I got it. So great watch for low clotting factor and platelets. Sorry for late response I work like 10 hours a day. :-).
I had a huge bruise on my ankle. It swelled to the size of a golf ball were I must have struck it. It was very painful and took a month to go down to yellow discoloration. I have no idea were I knocked it. It happens.
It's amazing how little damage is required to cause a big bruise. A slight bump that was so insignificant that you don't even remember it, can cause a good bruise, if you strike the right spot. Probably nothing to worry about unless it happens again and again.
It's only a side effect if you have low clotting factors including platelets. Since your recent lab work was fine, I wouldn't worry about it unless you keep getting more large bruises.