Where is the swelling?
When did you injure it?
Can you walk?
As I cannot examine you then I cannot give you a 100% diagnosis.
However if you can walk and you are happy that there is no fracture then you can stay at home - sprains can take 3 weeks to recover but there is always a chance that you may have a small " avulsion" fracture associated with it.
Please read the link that I have posted below.
A swollen calf is a symptom of a DVT ( blood clot), if your calf is swollen you need to go to the ER.
Here is some further info on DVT