The term "rest day" doesn't have to be taken literally; there are lots of things you can do today to help you reach your goals. If you find your muscles are tight and sore, try some foam rolling to massage the muscles, so you'll be ready to go tomorrow. Legs in particular respond well to movement after a leg workout, so taking a relaxing walk—even if it's just through the grocery store—can do wonders to relieve muscle tightness and discomfort.
There's a difference between sore muscles and an actual muscle injury. Some soreness and stiffness for a day or two after a tough workout is perfectly normal, and shouldn't be considered a reason to skip your next workout. However, if the pain is serious, or just feels wrong somehow, err on the side of caution and have it looked at.