What to do when your work/school requires a doctor's note but you're not even well enough to go to the doctor to get a note??

Fucked up my knee really bad yesterday, while doing a required task at school. Have been bedridden since noon yesterday, was planning on getting a doctor's note today because both my work and my school are extremely physically demanding and if my knee doesn't work, I am down for the count. But I can't even fucking walk now and I don't have anyone to take me to the doctor. What do I do?