Not a medical person but my ds had his plaster taken off after 6 weeks last year and he said his arm felt "really weird" and he didn't use it for a day or so. He was scared to carry anything too heavy or even write for a while. He said it felt weak.
I think give him a while to get used to not having it on. He'll probably forget about it if you relax and concentrate on other things, iyswim.
Could you take him swimming? That's supposed to be good for getting the muscles back working. hth
My DS (3.6) broke his leg in February - spiral fracture of the tibia acquired whilst messing about with Daddy! He spent 4 weeks in a full cast and 4 in a half-leg one. He charged around on the half-leg one - walking, running, scootering, etc. Most people didn't know he still had a cast on However when it was taken off he went back to shuffling around on his bottom and refusing to put weight on it at all. After a day or two we went out for the day and within minutes he wasn't sitting in the pushchair, he was pushing it!! He did walk with a very pronounced limp for a while and sometimes his leg was achey(!) but within 3-4 weeks you would never have known anything had ever been wrong.
Give your DS a bit of time, expect things to ache/hurt at times (his ankle has been in one position for 5 weeks so it will feel odd to move it) and find some distracting things to do. Soon you will be running to keep up again
Thanks for everyone's posts. Good to hear other peoples experiences. We're trying to encourage him slowly and he has tried to put his foot flat on the floor this morning. We're off swimming later - consultant said that would be good for him. He's desperate to ride his bike and play football - so he want's to get his leg working too!
Feetheart - my DS was just the same! With his leg in plaster he's played cricket, tennis, run (well hobbled!) around on the beach, been swimming. He adapated so well. Now it's back to bum shuffling and being carried everywhere. They said he was too young for crutches, so we got a wheelchair. He's had no nursery for last 5 weeks though -and he doesn't want to go back!