What does it mean when nerves jump in your arms like muscles is it anything to worry about?

Maybe, maybe not ... Muscle twitches in a few muscle fibers can start and stop on their own. The fibers don't create enough force to cause a big movement but the twitches are annoying. Some people report vibrations, which would be faster than twitches. Muscle cells do vibrate at certain frequencies during some kinds of contractions. A pm&r (physical medicine) doctor or neurologist who does muscle testing can evaluate.
Nerves do not jump. It is likely muscle fasiculations which can mean anything from fatigue, to dehydration to calcium or potassium levels to muscle or neurological disease. Most commonly spontaneous fascicualitons are due to metabolism, fluids and electrlolytes and occur after strenous exercise. If spontaneous fasciculaitons or muscles twithes seem to be present a lot or are increasing see your doctor soon.