On average it will push back the technology level to simple farmers or even more to gatherers/hunters.
Why? Modern lifestyle strongly depends on a network of abilities and competences shared among the population. Few of us can sew a clothe, build a motor, fix some electronic. We mostly rely on others to do it.
To make thing worse, most of the documentation on this knowledge is stored in major cities, which presumable have been wiped out by the war. So kids will grow up listening to elderly talking about airplanes, computers, smartphones and rockets and will take them as fairy tales.
So, we end up wit a still decent number of people (about 1 billion in total) who might know that something can be done (i.e. they might know that an open wound can be cured with antibiotics) but have no clue how to do it and cannot access any book or technology which can help them.
Probably who is already somehow related to farming will have an easier life, but also there issues will come soon: with the chemical industry gone, so are synthetic fertilizer and pesticides, so wave goodbye to high yields from the land. Also mechanicals aids will fade over time, further lowering available primary resources.
Small islands of higher technological knowledge will survive here and there based on the local variety of survivors. But also there our massive dependence from computers will ask its tribute. I.e. consider how engineers in the '60s built the Saturn V with just a sliding rule, while modern engineers (50 years later) would hardly be able of doing anything without a computer.