I have been told that I have a meniscal cyst. But in the past few days, my knee is in excrutiating agony to the point I can't bear weight. Help!

You need to see orth. You have a meniscal cyst and it is symptomatic and giving you excruciating pain causing you difficulty weight bearing. You may need arthroscopic surgery or intra articular decompression. So dont waste time and see your orthpedic surgeon asap.
Meniscal cyst. You have been told the cause of your pain. You need to see an orthopedist for evaluation and possible surgery.
Get checked. If has been hurting that much more, get checked again. You may have built up too much fluid, which can be drained. In the meantime, if you can, take some Ibuprofen and try keeping you leg up, so the fluid can drain down. (like sit in a recliner chair with your legs up and a pillow under your knee.) an ice pack on it for about 20 minutes every hour may help as well.