Fences blown down between my back garden and council house

The dividing fence between my private owned property and the empty council house next door has blown down in the back garden due to the recent storms, when I moved in 5 years ago and spoke to the elderly tenant next door he said the council put the fence up and the smooth side is indeed on the other side to mine. The problem is I have an autistic son who has a dog to help him who now can't go in the garden, plus my son has no concept of boundaries and could easily get hurt if he crossed over to next doors garden as it's very neglected with bottles on the ground. Please get in touch ASAP as what needs to be done thank you