Hi The Back Of My Knee Area Was Hit By

hi
the back of my knee area was hit by my car door that slammed into the back of my leg while putting groceries in the back seat .....I saw my dr but he said no worries its been 3 months and its still swollen
and I can walk but its bothersome..not sure what to do next Im on medicare and want to be sure if I go to er or walk in clinic they wont charge me.thank you