18 month old

So a couple days ago my lo was stumbling but he is an advanced walker. The advice nurse told me to go to the er but he felt better and they sent me home. Today. He got his vaccine (I belive the 15 month ones, sincey pediatrician recommended just for me to wait until 18 months because of my insurance) he was great the whole day and out of nowhere he was walking funny at 5pm. And he didn't want to put pressure on his foot/leg and held on to the table and did fed him and gave him a bath while talking to the advice nurse and trying to get a hold of my pediatrician. The guy who was on call told me that it happens (even if it was the leg he didn't feta shit on) and to give him Tylenol and if he doesn't feel better in 24 to contact them. Now after a bath and Tylenol it is 10 pm and he can't sleep well. Has this happened to anyone's lo before?