Last year, about a month after I had the fall flu shot, I had a dark pink, flat, asymmetrical spot appear on the inside of my calf. Very painful to touch, walk, etc. It faded and within 2 weeks another area cropped up down by my ankle, same leg. Went to ER because of my MG and thinking it could be blood clots. Not clots. They couldn't figure it out, sent me to rheumotology. Finding no other explanation, they thought it was erythema nodosa from the flu shot, possibly masked by the prednisone I'm on. The second area faded within a couple of weeks, and haven't had a problem since. I've decided not to get the flu shot this year.