You should wait until it's a LOT better, not just a little - don't want to break it down again while it's on the mend... lower leg sounds like
shin splints if you were running / jogging, your knee's take a hell of a hammering with those exercises too...your problem now to me sounds catilage related, I would advise you pop down to your local health store and buy some glucosamine and chondroitin and see how that works for you, mean while don't do any high impact sports that will aggrievate your knees.