I'm 21 weeks pregnant and have what looks like a hickey on my upper right thigh. What is it?

I certainly have not had anyone sucking on my leg, bumped into anything hard, or been pinched in the last few days, thus the reason for my concern. I cannot get a-hold of my doctor seeing as how its the weekend and I don't want to go into the ER and be looked at like I'm crazy if its nothing serious.