Toddler suddenly won't beat weight on one foot

[Sellingsunsets]

Took DS to nursery earlier, he was walking fine. Picked him up and he is refusing to walk on one foot or bare any weight on it. Nursery said he hasn't had a knock or a bang but noticed at dinner time he was walking on his knees. I've tried to get him to walk and he won't. He won't even put any weight on it properly. He hasn't got any marks or bruises or swelling. He is non verbal and autistic so he can't tell me he is in pain but he seems fine within himself, no other symptoms apart from the refusing to walk on it. Ive rang 111 and awaiting a call back but I'm quite worried. He normally walks on his tip toes and has done since forever but he's never had any pain or anything with it. Google said it could be serious. So I guess I'm just worrying. Anyone else had this with their toddler?

Has he been ill recently? My ds (was 6 at the time) stopped weight bearing on one leg very suddenly out of the blue. There was no sign of injury and he couldn’t remember hurting it in any way. Upon advice, I took him to the hospital as I was concerned that there was something serious going on. The drs did a whole lot of tests and scans but couldn’t see anything wrong with his leg or anything else sinister going on. They concluded that he had transient synovitis which is a temporary inflammation of the hip (which was triggered by a previous minor illness he’d had) which can affect various parts of the leg causing a limp or, in my son’s case, no weight bearing on one leg.