If you're having swelling in that leg also it could be something serious like a blood clot. If not it's probably a pinched nerve and should get better over time. Call your doctor if you have swelling and pain in one leg only.
It sounds like your baby is possibly laying funny on a nerve. When ive had things like that happen I'm pregnant with baby number six I tried pushing not to hard on baby toget them to move a bit. Sometimes it helped. Also heating pad not to hot for to long though.hope u feel better