Injury to leg... have a swollen knot on leg... how long will that last?

Swelling is generally inflammation and often associated with a muscle or tendon strain or sprain. R.I.C.E. is the first modality:

R=Rest. Refrain from activity which aggravates the condition.

I=Ice. Applying cold to the area reduces swelling and pain. Never
more than 10-15 minutes at a time.

C=Compression. Wrap an elastic bandage around the swollen
area to contain the swelling as the body absorbs the fluid.

E=Elevation. Keep the swollen area at about the level of the heart until the swelling starts to dissipate

If the swelling does not go down within a couple of days, you should see a MD as it could be related to something other than a strain or sprain. Things to consider are a popped muscle which can happen in the calf, or something related to a blood vessel..

abt 5 days with medication

I would see a doctor. There may be treatments that help, such as massage, or ultrasound and maybe others. Good luck!

Make sure you put ice on it regularly (10 minutes on, 10 minutes off) take some ibuprofen and keep it elevated. It should start to feel better in a day or two the knot should be gone in a week and the bruise a few weeks after that