Are there any good ways to stretch your lower left part of your back or knees?

Yes there are, BUT. You should get into a pt or an ath. Trainer so that you could be first assessed, then a specific exercise program, just for you, could be started and gradually build on that foundation. By the end of it, you achieved what you wanted, safely without hurting yourself in the process. Without supervision one can get hurt which may cause them to give up on such endeavours so get into one.