I injured my knee and i want to know what i should do?

Unable to answer: More details are needed in order to answer your question.

Have it evaluated: If the pain persists beyond a short period or if the knee is swollen, see an orthopedist. You may need an MRI to determine the cause.

Hmmmm.?: Depends. If it is mild then first line treatment is rest, ice , compression, and elevation. If bad, getting worse, or no better after a couple weeks then get it checked out.