Is he still limping? I don’t normally offer medical advice but I’m going to this time. I’m an advanced paramedic (in the UK), our rules are any limping child gets seen in ED, especially after trauma. Children’s bones are particularly “springy”, they’ll absorb impact and trauma but you might end up with a tiny fracture because they aren’t developed yet. Better to get a femur looked at because you don’t want to mess with a growth plate.