My 4 Year Old Son Has Had Croup. About 6

My 4 year old son has had croup. About 6 days ago it started and he had decadron that helped it. Yesterday we went sledding and that evening he started complaining of neck pain on the back of his neck. He also started his croupy cough again and fevered all night with it coming down while he was on meds. He complained of the neck pain mostly and when his fever was bad, but when it came down, he said his neck was feeling better. I'm a nurse so I'm used to the croup symptoms but I'm puzzled a little about the neck pain. Is it something that I should worry about? It could be whiplash from sledding?