Swelling from wasp sting on bottom of foot. Can’t walk.

Hi all. I’m a 37f approx 5’4” with no known allergies. I got stung by a yellow jacket 4 days ago on the bottom on my foot. It wasn’t too bad at first, and on Thursday I even went walking 5 miles with a friend. Come Friday, I can barely even walk or put pressure on it. It’s swollen and VERY sore. Is this normal? Or did I do a bunch of damage by walking 5 miles? Also, I’m pregnant so I can’t take ibuprofen. Should I go to the ER?