Nectarines suffer from the same disease as peaches, peach leaf curl. This is caused by a fungus carried in the rain. The best treatment is to spray with a copper based fungicide (if we are still allowed to buy those?) in the spring before the flowers open. This will help prevent.
In a good summer, the tree will make new leaves and outgrow the problem, though the fruit set may be affected.
The best way to protect the tree if it is fairly small, is to put a cover over it, even of plastic sheet, to protect it from the winter and spring rains.
We have a peach tree in a little protected area against a south facing wall and this never gets the disease, while all the ones in the garden do.

Thanks for your help . I have to hope then that next year will be better , I have been told that it was because I live on the coast and that it was the sea air that caused it.I will try your spray if I can get it Thanks again.