Go and get checked asap, could be a blood clot, very common as molly said above x
I was the same and this was in both legs, keep moving as much as you can. I took aspirin once a day too. I was so inactive in pregnancy my body was adjusting to movement again.
Please go to get checked out for a DVT asap. Really common after pregnancy and can be so dangerous/life threatening. Xx https://www.rcog.org.uk/for-the-public/browse-our-patient-information/diagnosis-and-treatment-of-venous-thrombosis-in-pregnancy-and-after-birth/#:~:text=it%20in%20pregnancy%3F-,Pregnancy%20increases%20your%20risk%20of%20a%20DVT%2C%20with%20the%20highest,including%20the%20first%203%20months.