It could also be sciatic nerve..
If you are not very active, there's a chance it could be a blood clot. Is it hot to the touch or have any discoloration??? Doctors encourage pregnant women to walk around a lot because blood clots can be easy to get. That's just worse case scenario though! Could be nothing! Our legs, feet, hands, etc swell and sometimes don't get great circulation. Try massaging it for awhile. If you have a serious concern, go to an urgent care !